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UNITED STATES OF AMERICA. 



LECTURE NOTES, 



GENERAL CHEMISTRY. 



NON-METALS. 




J. F. McGREGORY, A.M.^FK&f 

PROFESSOR OF CHEMISTRY IN COLGATE UNIVERSITY. 



HAMILTON, N. Y.: 
Republican Power Print. 

1894. 



COPYRIGHT, 1894, BY 
J. F. Mc GREGORY. 






Lecture Notes on General Chemistry. 



INTRODUCTION. 



i. Matter. All the objects by which we are 
surrounded, possess the common property of weight. 
By this we mean, that they are attracted toward 
the earth by the force which we call gravitation. 
Weight is common not only to all solid substances, 
such as stone, and all liquids, such as water, but 
also to all gases, such as air. We use the word 
matter to designate all such bodies. Matter, there- 
fore, is anything which possesses weight, and exists 
in three forms, the solid, the liquid, and the gase- 
ous. 

2. Force. There are certain changes which take 
place in matter which can be shown to be directly 
connected with a movement in the particles of mat- 
ter. These changes may be either temporary or 
permanent. That which imparts and thus causes 
the change we call force. Force, therefore, is that 
which is capable of producing motion in matter, or 
of altering the direction or velocity of matter al- 
ready in motion. 



2 LECTURE NOTES. 

3. Departments of Science. Matter may be stud- 
ied with reference to its external form or structure, 
its internal properties, its composition, or the 
changes which maybe produced by different forces. 
Many facts may be obtained by simple observation, 
while others require some test or experiment to 
show them. The knowledge thus derived and sys- 
tematized is embraced under the general head of 
natural science. 

Chemistry and physics have to do, not only with 
external and internal properties, but also with the 
changes which take place when matter is acted up- 
on by forces, and are often called the physical 
sciences. 

4. Definition of Chemistry and Physics. Chem- 
istry is that branch of physical science, which treats 
of the ultimate composition of matter, of the perma- 
nent changes which take place when matter is acted 
upon by forces, and of the action and reaction of 
different kinds of matter on each other. 

Physics is closely connected with chemistry, and 
is that branch of physical science, which treats of 
the temporary changes which take place when mat- 
ter is acted upon by forces, and of the nature and 
properties of the forces which produce the changes. 

5. Indestructibility of matter. Although many 
of the chemical changes which take place in matter 
often seem marvellous, and there appears to be 
a loss of substance, yet this is not the case, tor, 
matter can neither be created nor destroyed. The 



LECTURE NOTES. 3 

weight of the resulting substances can be shown to 
be exactly equal to the original matter. This is the 
principle of the iiidestructibility of matter. 

6. Divisions of matter. There are three divi- 
sions of matter recognized by modern science ; the 
mass the molecule and the atom. 

The mass is any portion of matter which can be 
appreciated by the senses. 

The molecule is the smallest particle into which 
the mass can be divided without losing its identity. 

The atom is the still smaller particle obtained by 
the ultimate division of the molecule. 

7. The attraction of mass. All masses possess 
a certain amount of attraction for each other. In 
comparatively small bodies this is inappreciable but 
is very great between the sun and planets and be- 
tween small bodies and the earth. This force is 
called gravitation, and is that which gives matter 
weight. 

The measure of this force is accomplished in two 
ways ; we may compare it with a unit weight of 
some substance which has been determined under 
fixed conditions ; or, we may compare it with an 
equal volume of some standard substance under fix- 
ed conditions. The former is called absolute, the 
latter relative weight. 

8. Weights and Measures. Modern science em- 
ploys the metric system of weights and measures. 

The standard unit is the meter, which is one ten- 



LECTURE NOTES. 



millionth of a quadrant of the meridian passing 
through Paris. It is equal to 39.37 inches. 

The unit of weight is the gram, -"hich is the 
weight of 1 cubit centimeter of pure water, at 4 
centigrade, and a barometric pressure of 760 milli- 
meters. This is equal to 15.43 grains avoirdupois. 

The unit of capacity is the liter, which is one 
cubic decimeter, or 1000 cubic centimeters. It is 
equal to 1.056 U. S. standard liquid quarts, or 61.02 
cubic inches. 

9. Specific gravity and density. These are the 
terms used to express relative, weight, that is, the 
weight of any substance compared with an equal 
volume of some substance taken as a standard. 

Specific gravity is the weight of solids or liquids 
compared with an equal volume of water, or, of 
gases compared with an equal volume of air. 

Density is the weight of any gas compared with 
an equal volume of hydrogen. 

iO. Diffusion of liquids and gases. Solid sub- 
stances can only be mixed together by mechanical 
force. When two or more liquids are brought to- 
gether, some mix readily while others do not mix 
at all. If two liquids which mix are brought to- 
gether carefully, they will remain separated for 
some time but will gradually become homogeneous. 
This gradual mixing is called diffusion. 

When gases are brought together, they always mix. 
and that quite rapidly, the rapidity being dependent 



LECTURE NOTES. 5 

upon the density of the gases. The rapidity with' 
which gases diffuse is found to be inversely propor- 
tional to the square root of their densities. 

ii. The effect of heat on matter. The effect of 
heat on all kinds of matter is to expand it. In the 
case of solids and liquids, the amount of expansion 
varies with the substance ; in the case of gases, the 
expansion is uniform. If the temperature of the 
gas be reduced to o° centigrade, it is found, that for 
each degree of increase of temperature, gases ex- 
pand 2T3- of their volume at o°. This number, g-l^, 
or its corresponding decimal, 0.003665, is called the 
co-efficient of expansion. 

To find the volume of any gas at any tempera- 
ture, if we let V represent the given volume, V x the 
required volume, t the degrees of temperature of the 
given volume, and t x the degrees of temperature of 
the required volume, we have, 

V: Vx :: 273 + t : 273 + t x . 

From this we obtain, 

Vx = v j 273 -f- t x \ 



■ 273. + jt y 

12. Thermometers. The fact that liquids ex- 
pand when heated, is utilized in the construction 
of the thermometer, which is an instrument for 
measuring temperature. It consists of a very nar- 
row glass tube with a bulb at one end, which is 
filled, usually, with mercury. The graduation of 
the tube is always from two fixed points, the melt- 



6 LECTURE NOTES. 

ing point of ice, and the boiling point of water. 
There are three thermometric scales, the centigrade, 
the Fahrenheit, and the Reaumur. 

The Centigrade is universally employed in scien- 
tific works, and being based on the decimal system, 
is the most rational and convenient in use. The 
melting point of ice, (commonly called the freezing 
point of water) is marked o°, and the boiling point 
ioo°. 

In the Fahrenheit scale, the zero is the point 
reached by the mercury when placed in a mixture 
of snow and*salt. The freezing point, is reached 
at 32 and the boiling point at 212 . 

The Reaumur scale fixes the freezing point at o° 
and the boiling point at 8o°. 

The relation of value between the degree of these 
different scales is expressed by the ratio of 5 to 9 to 
4, ioo° C. being equal to 180 F. and 8o° R. 

As it is often necessary to transfer from one scale 
to another, we make use of these relations to de- 
duce the following equations : — 

C.° = f (F°- 3 2°). C° = ^ R°. 
F.°=i C° + 32 . F = fR + 32, 

R° = 3 (F°- 3 2°). R°-iC°. 

The degrees below zero are designated by the 

minus sign. 

13. The Barometer. We have already noticed 
that gases have weight, [f this be true, theatmos- 



LECTURE NOTES. 7 

phere about us has weight, and must therefore exert 
a certain amount of pressure upon the surface of the 
earth. Moreover, since the particles of a gas move 
freely in all directions, the atmospheric pressure 
must vary at different times and elevations. 

An instrument for measuring the atmospheric 
pressure is called a barometer. This, as ordinarily 
constructed, consists of a tube, somewhat more than 
800 millimeters long, closed at one end, filled with 
mercury, and then inverted in a cup of mercury. 
The mercurial column, instead of filling the tube, 
will be seen to sink to a certain level. That this is 
due to atmospheric pressure, can be easily shown. 

Under ordinary conditions, and at the sea level, 
the column of mercury is about 760 m. m. in height. 
This is called the pressure of one atmosphere, and 
pressure is often measured in atmospheres. The 
amount of this pressure can be obtained absolutely, 
b} T using a tube with a cross section equal to one 
square centimeter, w T hen the weight of the mercu- 
rial column will be the amount of pressure on that 
amount of surface. This is found to be equal to 
1033.3 grams or one square centimeter, or about 15 
pounds on one square inch. 

14. The effect of pressure on matter. The effect 
of pressure is to decrease the volume of matter. In 
the case of solids and liquids the amount of the de- 
crease is exceedingly small. In the case of gases it 
is found that the decrease in volume is regular, un- 
der pressure, and that, when the pressure is removed, 



8 LECTURE NOTES. 

the gases expand to their original volume. The 
law of gaseous volume, so far as it is dependent up- 
on pressure is, that the volume of a gas is inversely 
proportional to the pressure to which it is subjected. 
In order to change the volume from any given to 
any required pressure, if we let V represent the giv- 
en volume under the barometric pressure B, and \\ 
the required volume under the pressure B x , we 
have: — 

V : Vx :: B x : B; or \\ = X -. 

B x 

If we wish to combine this correction of pressure 
with that for temperature, we have the following 
equation: — 

I 273 + t i B x 

15. Molecules. These are the minute particles 
which form the mass. They are composed of two 
or more atoms which are held together by the force 
of their mutual attractions. The molecules them- 
selves are held together by a strong force which 
acts only through a very small distance. Each 
molecule forms an independent group which acts 
as a unit until broken by some superior force. 

If the molecule consists of one kind of atoms 
only, it is called elementary ; if of more than one 
kind, it is called compound. Most elementary mol- 
ecules consist of two atoms. 

16. Molecular Attraction. By molecular attrac 



LECTURE NOTES. 9 

tion we mean the force which holds together the 
molecules in the mass. This force is called cohesion, 
when the molecules are of the same kind, and ad- 
hesion, when they are of different kinds. This 
force is very different in different molecules, and is 
strongest in some of the metals. 

That the molecules are in constant motion can be 
easily proven, although the motion in solids is very 
slow. This motion is due to an opposite, or repul- 
sive force, and the relations of these two forces, the 
attractive and repulsive, give us the three conditions 
or states of aggregation of matter, the solid, the li- 
quid and the gaseous. 

In solids, the molecules are very near together, 
molecular attraction is strong and the repulsive 
force weak, and there is very little motion among 
the molecules. 

In liquids, the molecules are not so near together, 
molecular attraction is much less, and the repulsive 
force much greater, (owing to this increased distance 
between the molecules,) and the molecules can move 
about more freely. 

In gases, the molecules are so far apart that mo- 
lecular attraction has ceased, the repulsive force is 
very great, there is perfect freedom of motion, and 
the molecules can only be controlled and limited in 
their motions by some external force. 

17. Molecular volume. By molecular volume 
we mean the amount of space occupied by the mol- 
ecules. 



IO LECTURE NOTES. 

In solids and liquids there is no general law of 
relation. In gases, the many ways in which they 
are similarly affected, leads to the very important 
deduction, that all molecules in the gaseous state 
occupy the same amount of space ; but since the 
amount of space a gas will occupy depends upon 
both temperature and pressure, the law is given as 
follows : — Under the same conditions of temperature 
and pressure, equal volumes of all kinds of matter 
in the gaseous state, contain the same number of 
molecules. This is known as the law of Avogadro. 

18. Molecular weight. Although the molecule 
is so small that we can only approximate its abso- 
lute weight, we can, by the application of Avoga- 
dro's law, obtain its relative weight. 

The molecular weight of a substance is the weight 
of the molecule, compared with the weight of one 
atom of hydrogen. Hydrogen being taken as the 
standard, the weight of its atom is one. Since 
equal volumes of gaseous matter, under the same- 
conditions of temperature and pressure, contain the 
same number of molecules, it follows that the weights 
of the molecules are in direct proportion to the 
weights of the whole volumes. If one of the sub- 
stances is hydrogen, this will give us the density of 
the gases; and since the number of atoms in the mol- 
ecule of hydrogen is two, [Art. 15.] the molecular 
weight can be obtained by multiplying the density 
of a gas by two. The molecular weight of a sub- 
stance can only be determined in the gaseous state. 



LECTURE NOTES. II 

19. Latent Heat. We have already seen that 
heat expands matter. This it does by weakening 
the molecular attraction, and thus driving the mol- 
ecules farther apart. 

The molecules, which are in a state of constant 
motion, can be acted upon by heat in two ways: — 
The velocity of their motion may be increased, the 
limits of molecular volume remain the same ; or, 
the limits of molecular volume may be increased, 
the velocity of their motion remaining the same. 
The former action results in an increase in the tem- 
perature of the body, and is called sensible heat, 
while the latter is always associated with a change 
in the state of aggregation, and, since it is not ac- 
companied by a rise in temperature, it is called lat- 
ent heat. Thus, a piece of ice at — io°, if subjected 
to heat, will grow warmer until it reaches o°. If 
the heating be continued there will be no further 
change in temperature until all of the ice is melted. 
[Increased limit of molecular volume.] The heat 
which melts the ice is rendered latent. 

If the water, formed, be now heated, the temper- 
ature will rise until it reaches ioo°, and the water 
begins to boil, after which, no further change in 
temperature will occur until all the water has been 
changed into steam. [Another increase in the lim- 
it of molecular volume.] The heat which is requir- 
ed to boil the water is rendered latent. After the 
steam has been formed, it can be heated with in- 
crease of temperature and volume the same as any 
other gas. 



12 LECTURE NOTES. 

20. Heat measurement. Sensible heat, or that 
which is shown by a rise of temperature, is meas- 
ured by the thermometer, but latent heat cannot be 
measured in this way. For this purpose another 
unit must be employed. This is the amount of 
heat necessary to raise a unit weight of water one 
degree of the thermometer, and is called a calorie. 

As there are different units of weight and differ- 
ent thermometers, we may have different heat units. 
For scientific measurements we use either the gram, 
or the kilogram, as the unit of weight, and the Cen- 
tigrade thermometer. The gram-calorie is the 
amount of heat necessary to raise one gram of wa- 
ter from o° to i° C, and the kilogram-calorie the 
amount necessary to raise one kilogram of water 
from o° to i.° C. 

21. Solutions. Solutions are homogeneous mix- 
tures which cannot be separated by mechanical 
means. Solutions may be formed between sub- 
stances in the same or in different states of aggre- 
gation. Two or more gases can always form a so- 
lution, and in all proportions, provided they do not 
unite chemically. Liquids very commonly form 
solutions with liquids, but not often in all propor- 
tions. The mixture of metals which we call alloys. 
may be considered as solutions of solids. Solutions 
of gases or solids in liquids, are most frequently ob- 
served. 

All gases dissolve in liquids to some extent, and 
in some cases the amount is very great. When no 



LECTURE NOTES. 13 

chemical action takes place, they can be expelled 
from the liquid by heating, or by diminishing the 
pressure. The degree of solubility depends upon 
temperature and pressure, low temperature, or high 
pressure, increasing the solubility. 

Solids are usually soluble in liquids to some extent, 
a high temperature usually increasing the degree of 
solubility. When the liquid is removed by evapo- 
ration the solid nearly always appears in the form 
of crystals. 

22. Atoms. Modern science assumes that the 
ultimate constitution of all matter is atomic ; that 
matter is made up of the exceedingly minute indi- 
visible particles called atoms, which are held to- 
gether by a very strong force. The atom has been 
defined as the particle obtained by the ultimate di- 
vision of the molecule, and is the smallest portion 
of matter which can enter into composition. 

There are at present over seventy different kinds 
of atoms known. These are called the elements, 
and include all such bodies, as cannot by any known 
methods, be decomposed into simpler substances. 
When different kinds of atoms combine they form 
what are called compounds. 

23. Atomic Attraction. The force which holds 
together atoms in the molecule is known as chemi- 
cal affinity, or chemism. This force varies greatly 
with the kind of atoms, but is constant for the same 
kind of atoms under the same conditions. 

This force can only act through minute distances, 



14 LECTURE NOTES. 

hence, any outside force which tends to increase the 
distance between the atoms weakens the atomic at- 
traction. As heat does this, chemical change takes 
place more easily at high than at low temperatures. 
Atoms of the same kind attract each other, but this 
attraction is less than that which exists between 
atoms of a different kind. 

When two or more elements combine to form a 
compound experiment shows that for a given com- 
pound it always requires precisely the same ele- 
ments in exactly the same proportions. This is 
called the law of definite proportions. When the 
same elements unite to form several compounds, the 
higher proportions of each, are exact multiples of 
the lowest. This is called the law of multiple pro- 
portions. 

24. Nascent state of atoms. Since atoms of the 
same kind have attractions for each other, they do 
not ordinarily exist alone. They may be- made to 
assume this condition for an instant of time during 
the process of chemical change. While in this con- 
dition they exhibit greatly intensified affinities, so 
that many chemical changes can be effected, which 
could not, under ordinary conditions, be accom- 
plished. This condition of intensified activity 
which the atoms assume before combination with 
other atoms, is known as the nascent state. 

25. Atomic weight. The atom, like the mole- 
cule, is so small that we can only approximate its 
absolute weight; but from the relations of the mol- 



LECTURE NOTES. 1 5 

ecule both toward other molecules and toward 
atoms, we can obtain the relative weight of atoms 
very exactly. These have all been very carefully 
determined and we define atomic weight as the 
weight of an atom of an}^ element compared with 
the w r eight of an atom of hydrogen, that being the 
lightest atom known. Sometimes the atomic weight 
is taken by comparison with oxygen, since oxygen 
forms compounds with nearly every element known. 
If the atomic weight of hydrogen is i, that of oxy- 
gen is 15.88, and if oxygen is taken as 16, hydrogen 
is 1.007. 

26. Atomic value. In observing the different 
compounds we shall see that a given element may 
require one, two, three or even more atoms of some 
other kind in order to satisfy its chemism. This 
quantitative value in chemical force is called val- 
ence. The measure of valence is the hydrogen 
atom, and those atoms which require one atom of 
hydrogen are called monads and are said to be uni- 
valent ; those requiring two hydrogen atoms are 
called dyads, and are said to be bivalent. 

Those having a higher valence are called triads, 
tetrads, &c, and are said to be trivalent, quadriva- 
lent, &c. One atom of hydrogen will thus unite 
with one monad element, and can never take more, 
each being satisfied. One dyad atom will require 
two, and one triad atom three monads, &c, while 
tw 7 o triad atoms will require three dyads. The val- 
ence of an atom is sometimes expressed graphically 



1 6 LECTURE NOTES. 

by certain marks placed above the symbol repre- 
senting the atom, thus: — CI', Ba", N'", &c. 

The valence of many atoms depends upon the 
temperature at which the union takes place, and 
also upon the kind of atoms entering into combina- 
tion. A variation in valence is quite often seen in 
the union of atoms with oxygen. When a varia- 
tion is noticed it is generally found to be increased 
by low temperature. The atoms which exhibit this 
variation, form with certain elements, like oxygen, 
what are called unsatisfied molecules. These usu- 
ally combine readily with additional atoms. 

27. Names and symbols of the elements. The 
names of the elements are given them by their dis- 
coverers, either from some peculiar property of the 
element, or from something connected with its dis- 
covery. Fur convenience in representing it, each 
element has an abbreviation of its name which is 
called its symbol. This consists of the initial letter 
of its Latin name, and, when necessary, of another 
distinctive letter, thus: — H for hydrogen, C for car- 
bon, CI for chlorine, Cu for copper, (cuprum 
The following is a list of the elements known, to- 
gether with their symbols and approximate atomic 
weights : 



LECTURE NOTES. 



Aluminum Al. 

Antimony 

(Stibium) Sb. 

Arsenic As. 

Barium Ba. 

Bismuth Bi. 

Boron B. 

Bromin Br. 

Cadmium Cd. 

Calcium Ca. 

Carbon C. 

Cerium Ce. 

Cesium Cs. 

Chlorin CI. 

Chromium Cr. 

Cobalt Co. 

Columbium- Cb. 

Copper (Cuprum). Cu. 

Erbium Er. 

Fluorin F. 

Gallium Ga. 

Germanium Ge 

Glueinum Gl. 

Gold(Aurum) Au. 

Hydrogen H. 

Indium In. 

Iodin I. 

Iridium — Ir. 

Iron v Ferrum) Fe. 

Lanthanum--. La. 

Lead (Plumbum)-. Pb. 

Lithium Li. 

Magnesium Mg. 

Manganese Mn. 

Mercury 

(Hydrargyrum) Hg. 
Molybdenum jMo. 



27. 

120. 

75- 
137- 
208. 

11. 

79^ 

112. j 
40. I 
12. i 

140.5! 

133- I 



52 
59 
94- 

63. 

166, 

*9- 

70. 
72. 

9- 

190. 
1. 

"3- 

126. 

193- 

56. 

13S. 

206. 

7- 

24, 

55- 

200. 
96. 



Neodymium 

Nickel 

Nitrogen 

Osmium 

Oxygen 

Palladium 

Phosphorus 

9 Platinum 

Potassium 

(Kaliuru) 

; Praseodymium 

Rhodium 

Rubidium 

4 Ruthenium 

3 Samarium 

Scandium 

! Selenium 

6 Silicon «.___ 

Silver (Argentum ' 
Sodium (Natrium) 

Strontium 

Sulfur 

1 Tantalum 

7 TELLURIUM--- 
! Terbium 

7 Thallium 

8 Thorium 

' Tin (Stannum) 

Titanium 

8 Tungsten 



(Wolfram) 

Uranium 

Vanadium 

I Ytterbium 

j |Yttrium 

1 Zinc 

; Zirconium 



Nd. 

Ni. 

N. 

Os. 

O. 

Pd. 

P. 

Pt. 

K. 

Pr. 

Rh. 

Rb. 

Ru. 

Sm. 

Sc. 

Se. 

Si. 

Ag- 

Na. 

Sr. 

S. 

Ta. 

Te. 

Tb. 

Tl. 

Th. 

Sn. 

Ti. 

W. 

U. 

V. 

Yb. 

Y. 

Zn. 

Zr. 



l8 LECTURE NOTES. 

28. Classification of the Elements. There are 
several ways in which the elements may be classi- 
fied. The most common classification depends up- 
on their possessing certain physical and chemical 
properties, and divides them, thus, into the two 
general classes, metals and ?io?i-metals. 

The principal physical characteristics of metals 
are, hardness, high specific gravity, lustre, and con- 
ductivity of heat and electricity. A few of the non- 
metals have some of these properties. Chemically, 
the non-metals form compounds with oxygen which 
dissolve in water and are then called acids, while 
the metallic oxygen compounds are called bases. 

There is, therefore, no very well defined line of 
separation between the two classes, and the one 
gradually merges into the other, so that the divi- 
sion is quite arbitrary. The element arsenic, for 
example, occupies an intermediate position, and is 
classed by some among the metals, by others among 
the non-metals. The non-metallic elements arc 
indicated in the table by being printed in small 
capitals. 

For convenience of description and reference, the 
elements are often arranged in groups, each group 
consisting of those elements which are more or less 
closely allied to each other. 

When an electric current is passed through 
lution of a chemical compound, decomposition takes 
place, a part of the atoms appearing at the positive 
and a part at the negative pole. Those which ap- 



LECTURE NOTES. 19 

pear at the negative pole are called electro-positive 
or positive atoms, and those at the positive pole, 
electro-negative or negative atoms. 

This distinction is entirely relative, for, while the 
metals, as a class, are positive, and the non-metals 
negative, an element may be positive compared 
with one element and negative compared with an- 
other. The greater difference the atoms of a com- 
pound may exhibit in their electrical affinities, the 
more powerful are their attractions for each other, 
and the more stable is the compound. 

By far the most complete and logical classifica- 
tion of the elements, is according to their increas- 
ing atomic weights. Thus arranged, the elements 
form regular periods and groups, and it is found 
that their general properties and valence are peri- 
odic functions of their atomic weights. A more 
careful examination of this most interesting classi- 
fication, belongs to a more advanced course of 
study. 

29. Chemical notation. Just as we can repre- 
sent each element by a symbol, so we can repre- 
sent each compound by a combination of symbols. 
This representation of a compound is called its 
molecular, or chemical formula. 

There are two ways in which a chemical formula 
may be written ; the symbol for each atom may be 
repeated as many times as it occurs, or the number 
of each kind of atoms which occur in the compound, 
if more than one, may be shown by a small nume- 



20 LECTURE NOTES. 

ral placed at the right and a little below each sym- 
bol. The latter is called an empirical formula , and 
is the one commonly used, while the former at- 
tempts to show the result of investigation as to the 
mutual relations of the atoms, and is called a con- 
stitutional, ox graphic formula. The valence of each 
atom, in a graphic formula, is expressed by little 
lines, connecting it to the other atoms; thus the 
compound, sulfuric acid, is expressed empirically 
as H2 SO4, while its graphic formula is 
H— CK Q ^0 
H— O >b ^O, 
One large numeral placed before the whole or a 
part of a formula denotes that the portion that fol- 
lows is to be repeated as many times as expressed 
by the numeral ; thus, 2C11SO4 means two mole- 
cules of copper sulfate. A numeral placed before 
or after a parenthesis affects all thesymbols within. 

30. Compound radicals. There are certain 
groups of atoms which play the part of single 
atoms ; for, while they do not often exist alone, 
they are found as never-varying constituents in cer- 
tain series of compounds, can be replaced in such 
compounds by other simple bodies, and, when in 
composition with a simple body, the latter can be 
replaced by other simple bodies. Such a group o\ 
atoms is called a compound radical. 

The compound radicals are classified according 
to their properties, and also according to their val- 
ence, and in many ways are treated just as it they 
were elements. 



LECTURE NOTES. 21 

One of the most important of the compound rad- 
icals is the monad group ( — O — H), called the hy- 
dro xy I group. This group occurs in a multitude of 
compounds, being sometimes united to a metal and 
sometimes to a non-metal, and imparting charac- 
teristic properties to each. 

31. Acids. The name acid is given to those 
compounds which are sour to the taste, and which 
change blue litmus paper, or other vegetable blues, 
to red. The}' all contain hydrogen combined with 
a negative atom or radical, and usually by means 
of oxygen. Those which contain no oxygen are 
few in number, and are called halogen acids, while 
those containing oxygen are called oxy-acids. 

The hydrogen in an acid is partly, or entirely, 
capable of being replaced by a positive element, or 
radical. In the case of the oxy-acids, the hydro- 
gen, which is replaceable, is joined to the negative 
part by means of oxygen, that is, it forms with the 
oxygen an hydroxyl group. 

The basicity of an acid is a term which refers to 
the number of replaceable hydrogen atoms which 
the acid contains, and this is therefore equal to the 
number of hydroxyl groups which it contains. An 
acid is thus called mono-basic, di-basic, tri-basic, 
&c, as it contains one, two, three, or more hy- 
droxyl groups, or atoms of replaceable hydrogen. 

32. Bases and alkalies. A base is a compound 
consisting of a positive element, or radical, with 
hydrogen and oxygen. A base will change vege- 



22 LECTURE NOTES. 

table reds to blue, will combine with acids so as to 
neutralize their effect, and have, when soluble in 
water, a peculiar soapy taste and feel. The name 
alkali is often applied to those bases which are of a 
specially active nature, and which are soluble in 
water. 

33. Salts. When an acid and base react on 
each other, the hydrogen of the acid is partly or 
entirely replaced by the positive part of the base, 
and a compound formed which is called a salt. Wa- 
ter is also formed in this process. A salt is, there- 
fore, a compound produced by the union of a me- 
tal, or positive radical, and a non-metal, or negative 
radical. 

If the metal replaces all of the hydrogen capable 
of being replaced, there is formed a normal salt. 
Such salts do not usually affect vegetable colors. 
If part of the replaceable hydrogen of the acid re- 
mains in the compound, there is formed an acid 
salt. Acid salts usually change vegetable blues to 
red, like an acid. 

There are certain oxy-acids which have the pow- 
er, in connection with certain bases, of combining 
with more of the base than is necessary to produce 
a normal salt. These, therefore, contain a very 
large proportion of base and are called basic salts. 
The principal acids which exhibit this property arc 
sulfuric, nitric, and carbonic acids, and the princi- 
pal bases, are those of lead, mercury, copper, bis- 
muth, antimony, and zinc. 



LECTURE NOTES. 23 

34. Modes of chemical action. There are seve- 
ral ways in which chemical action may take place. 
Two or more elements, or simple molecules, may 
unite to form a more complex one. Such an action 
we call synthesis. 

The degree of chemical activity differs gfeatly 
with the different elements. If an element, pos- 
sessing powerful affinities, comes in contact with a 
compound, it quite frequently happens that it dis- 
places an element or radical in the compound, and 
a new compound results. When two compound; 
come together it often happens that the conditions 
are such as to bring about an exchange of their 
constituent elements. Such an action we call me- 
tathesis. There are many causes which may result 
in metathesis. 

A compound may be decomposed by heat, or 
some other force, so as to form two or more simple 
compounds, or the compound may even be resolv- 
ed into its elements. This action we call analysis. 

In order to effect a chemical change it is necessa- 
ry to have actual contact between the molecules ; 
and since contact cannot often be secured between 
solids, the liquid or gaseous state is more favorable 
to chemical change. Solids can be brought into the 
liquid state by solution or fusion. 

35. Chemical equations. The chemical changes 
which occur when molecules are brought together 
may be expressed by what we call a chemical equa- 
tion, in which the formulas of the molecule brought 



24 LECTURE NOTES. 

together are placed before the sign of equality and 
called factors, while the formulas of the resulting 
molecules follow the sign of equality, and are call- 
ed products. 

In a chemical equation, since there can be no loss 
of matter, every atom of the factors must be account- 
ed for in the products ; and since the atomic weights 
are permanent, it follows that the sum of the mole- 
cular weights of the products must alway equal the 
sum of the molecular weights of the factors. The 
following will serve as an illustration: 

AgN0 3 + NaCl = AgCl + NaNOg. 

137-9 + 53.4 = H3-3 +53- 

36. Chemical nomenclature. Until nearly the 
end of the last century, only arbitrary names were 
given to elements and compounds, and those com- 
pounds which had some real or fancied resemblances 
existing between .their physical properties, were 
classed under the same general head. The first at- 
tempt at a systematic nomenclature, was made by 
Lavoisier, in 1787, and this system, with only 
slight modifications, is in use at the present time. 

No attempt was made to change the old common 
names of the elements, but, by common consent, 
the names of all recently discovered metals end in 
ium. 

A few of the old common names of compounds 
have been preserved. 

Those substances which contain only two ele- 
ments, or radicals, are called binary compound*. 



LECTURE NOTES. 25 

The names of the metal, or positive part, is writ- 
ten first, and the name of the non-metal, or nega- 
tive part, follows, with the last one or two syllables 
changed to id. Should more than one compound 
exist between the same elements, the name of the 
metal receives a new termination and becomes ic, 
or ous, the former indicating that the compound 
has the greater amount of the negative part. 

The name of an acid is derived from the principal 
element, and ends in ic, or ous, these terminations 
having the same signification as in binary com- 
pounds. Should more than two acids occur with 
the same principal element, the prefix hypo, (un- 
der), is used, if the acid contains less oxygen than 
the one with the name ending in ous ; thus, HClOo 
is chlorous acid, and HCIO, hypochlorous acid. 
Should an acid contain more oxygen than the one 
with the name ending in ic, the prefix hyper ox per, 
(above), is used; thus, HCIO3 is chloric acid, and 
HCIO4, perchloric acid. 

The name of a salt is taken from that of the acid 
from which the salt is derived. If the name of the 
acid ends in ic, the name of the salt will end in ate; 
and if the name of the acid end in ous, the name of 
the salt will end in ite. If the name of the acid has 
a prefix, the name of the salt will have the same 
prefix. The name of the metal contained in the 
salt remains unchanged except in the case where it 
forms two salts with the same acid, when the name 
is changed by terminations the same as in binary 



26 LECTURE NOTES. 

compounds; thus, a salt of sulfuric acid and iron. 
would in general be called iron sulfate ; but, since 
there are two compounds of iron and sulfuric acid, 
we call FeS0 4 , ferrous sulfate, and Fe-/ S0 4 )3, fer- 
ric sulfate. 



THE NON-METALS. 



Hydrogen. Symbol, H. Atomic weight, i. Spe- 
cific gravity, 0.0695. 

37. History and Occurrence. Hydrogen was 
discovered by Paracelsus in the early part of the 
sixteenth century. It was first accurately describ- 
ed by Cavendish in 1766, and called by him "in- 
flammable air." A few years later, Lavoisier 
showed its relations to oxygen in water, and gave it 
the name hydrogen. 

Hydrogen occurs free in the gases issuing from 
certain volcanoes, and, mixed with other gases, in 
natural gas. By means of the spectroscope, it is 
found to exist free in the atmosphere of the sun and 
many of the fixed stars. 

It occurs combined in water, in many of the 
rocks, and in all animal and vegetable compounds. 

38. Preparation. Hydrogen may be prepared in 
many ways, the most common method being, to dis- 
place it in some acid by means ol some metal. Or- 
dinarily we use zinc and sulfuric acid and the ac- 
tion is shown by the following equacion : 

Zn -f H,S0 4 = ZnS0 4 + H 2 . 
Water may be decomposed into its elements by 
means of the electric current, hydrogen appearing 
at the negative pole, thus: 



28 LECTURE NOTES. 

2 H 2 = 2 H 2 + 02. 

If certain metals, such as sodium or potassium, 
are brought in contact with water at the ordinary 
temperature, a part of the hydrogen will be dis- 
placed by the metal and come off free, thus : 
Na 2 + 2 H 2 = 2 NaOH + H 2 . 

Other elements, such as zinc, iron, or carbon, 
will decompose water at a high temperature giving 
hydrogen, thus : 

Zn + H 2 = ZnO + H 2 . 

39. Properties. Hydrogen is a gas, colorless, 
odorless when pure, and tasteless. It is the light- 
est form of matter known, being 14.48 times as 
light as the air. The weight of 1 liter of the gas 
at O and 760 m. m. pressure, is 0.0896 grams. 
This is called a crith. It is, on account of its light- 
ness, used as the standard for density. 

Pure hydrogen is not poisonous, and may be 
breathed for a short time without injury, but long 
continued breathing of the gas would cause death 
from suffocation. It is an inflammable gas, burn- 
ing, when pure, with a pale blue flame, which gives 
very little light, but great heat. It does not sup- 
port combustion, and a lighted taper is at once ex- 
tinguished when plunged into the gas. 

The burning of hydrogen is due to its combina- 
tion with oxygen and the formation of water, thus : 
2 H 2 + Oa = 2 H 2 0. 

Hydrogen has great affinity for oxygen and 



LECTURE NOTES. 29 

chlorin, and forms compounds with all the non-me- 
tallic elements, in which it acts like a metal. 
When subjected to great cold and pressure, it may 
be condensed to a colorless liquid. 

Hydrogen will diffuse itself through certain red 
hot metals, such as iron, platinum, and palladium. 
These metals will retain a certain amount of the 
gas when cooled, the metal palladium retaining 935 
volumes. This property has been termed occlusion 
by Graham, and, for various reasons, it is supposed 
that the hydrogen exists in them in the solid state 
and forms thus an alloy with the palladium. The 
name hydrogenium, has been given to this form of 
hydrogen. 

Oxygen. Symbol, 0. Atomic weight, 16. 

40. History and Occurrence. ' Oxygen was dis- 
covered in 1774 b)^ Priestley, who obtained it by 
heating mercuric oxid. A little later it was dis- 
covered independently by Scheele. Lavoisier gave 
it the name oxygen. 

Oxygen is the most abundant element in nature. 
It occurs free in the atmosphere, of which it forms 
about 23 per cent, by weight. Combined with 
hydrogen, it forms water, which is 88.87 P er cent, 
oxygen. Combined with other elements, it is found 
in nearly all animal and vegetable matter, and con- 
stitutes about 48 per cent, of the earth's crust. The 
whole earth, including the surrounding atmosphere, 
is about 50 per cent, oxygen. 



30 LECTURE NOTES. 

41. Preparation. Oxygen may be prepared from 
many of its compounds with the metals, and from 
its more complex compounds. It is usually pre- 
pared by heating the compound, potassium chlo- 
rate. The chemical equation for the action is as 
follows : 

2 KClOa = 2 KC1 + 3O2. 

This action takes place at a high temperature, 
and then with great rapidity. In order to obtain 
the gas at a lower temperature, and to avoid any 
danger from too rapid decomposition, about 10 per 
cent, of manganese dioxid, MnOs, is added to the 
potassium chlorate. This causes the gas to be giv- 
en off at a much lower temperature and more reg- 
ularly, and the M11O2 is found unchanged after the 
reaction. Just why this, and some other sub- 
stances, act in this way, is not well understood. 

When water is decomposed by electrolysis, oxy 
gen appears at the positive pole. 

Mercuric oxid, HgO, when heated, yields all of 
its oxygen, thus : 

2 HgO = 2 Hg -f Oj. 

Certain of the higher oxids, such as manganese 
dioxid, M11O2, and lead dioxid, PbOa, give off a 
part of their oxygen by heat, the former leaving 
mangano-manganic oxid, Mii:;0 4 , and the latter 
lead oxid, PbO, in addition to the oxygen. 

42. Properties. Oxygen is a gas. colorless, 
odorless, and tasteless. It is slightly heavier than 



LECTURE NOTES. 3 1 

air, its specific gravity being 1.104. It is only very- 
si ightly soluble in water, and when subjected to 
very great cold and pressure it condenses to a 
transparent liquid. It forms compounds, which 
are called oxids, with every other element except 
fluorin, and manj^ of these can be obtained by direct 
union of the elements, at a sufficiently high temper- 
ature. Oxygen does not burn, but it supports the 
combustion of inflammable substances with great 
vigor. Combustion, in the ordinary use of the 
term, is union with oxygen which is attended with 
light and heat. As the products of combustion are 
oxids, combustion is often called oxidation. Oxy- 
gen is necessary to all animal life. In the process 
of respiration the blood is purified by oxidation, and 
the waste products are thrown off through the lungs. 

43. Oxidizing and Reducing Agents. An oxidiz- 
ing agent is a substance which causes an element 
or compound to combine with oxygen, or with 
other elements'of a similar nature. Oxidation usu- 
ally changes an element from a lower to a higher 
state of valence. The most common oxidizing 
agents are, oxygen, chlorin, potassium chlorate, 
nitric acid, and hydrogen dioxid. 

There are certain substances which act in a way 
exactly opposite to that of oxidizing agents, and 
so remove oxygen, or elements of a similar nature, 
from compounds. These are called reducing 
agents, and usually change an element from a high 
to its lowest state of valence, or separate an element 



32 LECTURE NOTES. 

from its compounds. The most common reducing 
agents are, hydrogen, (particularly in the nascent 
state,) carbon, sulphur dioxid, and hydrogen sulfid. 
A clear understanding of these two actions is very 
important to a student of chemistry. 

Ozone (Allotropic Oxygen). Molecular formula, 0,. 
Density, 24. 

44. History and Occurrence. The peculiar pdor 
which is found in the vicinity of an electric ma- 
chine, when in use, and which follows an electric 
discharge through oxygen, was for a long time a 
puzzle to chemists. It was not until 1840 that this 
substance was thoroughly investigated by Sehon- 
bein, who showed it to be a peculiar form of oxy- 
gen, which he called ozone. 

Ozone is an allotropic form of oxygen. When a 
substance exists under two or more physical modi- 
fications, these are called allotropic forms. The 
allotropy, in the case of ozone, is due to the fact, 
that its molecule contains three atoms. 

Ozone is found in very small quantities, free, in 
the atmosphere, where it is produced by the elec- 
tric discharges during a thunder storm, also, proba- 
bly, by the growth of plants, and the lashing of 
waves. As it is a very energetic oxidizing agent, 
it is found most where the air is purest, as in the 
country, on the sea, and at high altitudes. 

45. Preparation. It is best prepared by the ac- 
tion of a silent electric discharge on oxygen. An 



LECTURE NOTES. 33 

instrument used for preparing it in this way is call- 
ed an ozonometer. 

It is evolved at the positive pole in the eleetrol} 7 - 
sis of water. 

It is formed by the slow oxidation of phosphorus, 
and many other substances, and by the decomposi- 
tion of certain highly oxidized compounds by 
means of sulfuric acid. 

46. Properties. Ozone is a gas, having a den- 
sity just one and a half times that of oxygen. It 
has a peculiar odor, a little like very dilute chlo- 
rin. Chemically, it is like oxygen, only with in- 
tensified properties. It oxidizes mercury, and sil- 
ver in the cold, and liberates iodin from its com- 
pounds. Only about five or six per cent of oxygen 
can be changed into ozone, because the ozone mole- 
cules decompose when brought into too close prox- 
imity with each other. Ozone decomposes slowly 
at the ordinary temperature, and instantly at about 
300 , forming ordinary oxygen. 

COMPOUNDS OF OXYGEN WITH HYDROGEN. 

There are two compounds of these elements, 
Hydrogen monoxid, or Water, H 2 0, and 
Hydrogen dioxid, or peroxid, H2O2. 

Water. Molecular formula, H_> 0. Molecular weight, 
18. Density, (of steam), 9. Specific Gravity, 1. 



34 LECTURE NOTES. 

47. History and Occurrence. Water was sup- 
posed, by the Ancients and the Alchemists, to 

be an element, and it was not until 1776, that La- 
voisier proved it to be a compound. Five years 
later, Cavendish proved it to be composed of hy- 
drogen and oxygen only, and in 1S05, Gay-Lussac 
proved the volumetric relations of its constituents. 
Water is the most abundant compound in nature. 
It is found free in the atmosphere, the amount be- 
ing dependent upon the temperature, and forming 
a relatively small, but important part of that body. 
It is found in large quantities, both upon, and 
within the crust of the earth. As water of crystal- 
lization it forms a necessary part of many mineral 
and chemical compounds. It is found in all animal 
and vegetable compounds, being necessary to all 
animal and plant life and growth. 

48. Preparation. Water may be prepared by 
the direct union of its elements, that is, syntheti- 
cally, by burning hydrogen in the air or in oxy- 
gen. 

When the two gases are mixed in the proportion 
of two volumes of hydrogen to one of oxygen, they 
can be made to unite by a flame, or an electric 
spark, or by heating to about 6oo°, and the union 
is attended with violent explosion. If hydrogen 
is burned in a jet with oxygen, the heat is the most 
intense which can be obtained by combustion. 

Water can be prepared by the oxidation of com- 
pounds containing hydrogen, and hence it is always 



LECTURE NOTES. 35 

found as a product of the deca3^ or burning, of all 
animal or vegetable substances, and is thrown off 
by the lungs in the process of respiration. 

It is also formed in the reduction of many of the 
oxids of the metals, by means of hydrogen, thus : 
CuO + H 2 = Cu -f H 2 0. 

49. Properties. Water is a liquid, at the ordi- 
nary temperature, and, when pure, has neither 
odor nor taste. It is apparently colorless, although 
in large quantities it has a distinctly greenish blue 
color. 

It has no action upon vegetable colors, and is a 
poor conductor of heat, and a worse conductor of 
electricity. Water is the most valuable solvent 
known. It not only dissolves many solids, but 
many liquids mix with it in all proportions. It 
dissolves all gases to some extent, and many in 
large proportions. On this account, water is never 
found quite pure in nature. The natural waters 
are usually pure enough for most purposes, and if 
pure water is required, it can be obtained by the 
process of distillation. 

Pure water is taken as the standard for the spe- 
cific gravity of solids and liquids, and is used to ob- 
tain the unit of absolute weight in the metric sys- 
tem. (See Art. 8.) 

Water forms a curious and important exception 
to the general law that matter expands by heat : 
for, if water is heated from o° to 4 , it is found not 
to expand, but to contract. Above 4 it begins to 



36 LECTURE NOTES. 

expand, and continues to do so, although the ex- 
pansion is very irregular, being greatest at about 
30 . This peculiarity in the expansion and con- 
traction of water is expressed by saying, that the 
point of maximum density of water is 4 . 

Although the amount of contraction from o° to 
4 is very small, it is one of the most important 
facts in nature. It is for this reason that water 
freezes on the surface, and not on the bottom, as is 
the case with most liquids. If this were not so, 
our climate would soon become frigid ; for our 
lakes and rivers would freeze solid in winter, and 
the summer heat would not suffice to melt the ice. 

Water usually becomes a solid, that is, freezes, 
at o°. At the moment of becoming solid it in- 
creases about ^ Y in bulk, the specific gravity of ice 
being 0.916. This is another important fact in na- 
ture, and is the principal cause of the disintegra- 
tion of the rocks, and the formation of soil- 

If water be carefully cooled, the temperature 
may often be reduced to some degrees below zero 
before the water is frozen. The melting point of 
ice is always o°, hence this is taken as one of the 
fixed points on the therinometrie scale. When 
water is heated to ioo°, it forms a gas which we 
call steam. Steam acts like a true gas and obeys 
all the laws of gases. 

50. Latent heat of Water and Steam. We have 
already noticed, (Art. 19.) that when ice is melted 
or water boiled, much heat is rendered latent. The 



LECTURE NOTES. 37 

amount of heat thus rendered latent, can be approx- 
imately determined as follows : If we should mix i 
kilogram of water at o°, and i kilo, at 79 , there 
would result 2 kilos, of water at a temperature of 
39. 5 ; but if we mix 1 kilo, of ice at o° and 1 kilo, 
of water at 79 , there will result 2 kilos, of water 
at o°, that is, the ice will just be melted. It has, 
therefore, taken the quantity of heat necessary to 
raise the temperature of the water from o° to 79 , 
to melt the ice. (Art. 20.) Hence the latent heat of 
water is said to be 79 thermal units, or calories. 

If we lead steam from boiling water, at a temper- 
ature of ioo°, into 1 kilo, of water at o°, until the 
water boils, that is, until it is heated to ioo°, the 
steam is found to have condensed in the water un- 
til it now weighs 1.187 kilos. This means that 
0.187 kilo, of steam at ioo°, has raised the temper- 
ature of 1 kilo, of water, from o° to ioo° ; or, 1 
kilo, of steam would raise 5.36 kilos, of water from 
o° to ioo°, or 536 kilos, from o° to i°. Hence the 
latent heat of steam is said to be 536 thermal units, 
or calories. The heat which is rendered latent in 
the formation of steam, is manifested as tempera- 
ture when the steam is condensed to water ; and, 
since there are 536 units of heat to be liberated, 
steam is found to be very effective in the heating of 
buildings. 

51. The Tension of Aqueous Vapor. If we allow 
a glass of water to stand in a room for a number of 
days, the water will disappear, or evaporate, as we 



38 LECTURE NOTES. 

say. Even ice, if exposed to the atmosphere at a 
temperature below the freezing point, will evapo- 
rate. This power of water to pass into the form of 
vapor at all temperatures is called the clastic force, 
or tension, of aqueous vapor. The vapor, which is 
thus given off, exerts a certain amount of pressure, 
which increases with the temperature; and if the 
temperature is increased to the boiling point, the 
tension or pressure of the vapor just equals the at- 
mospheric pressure. From this it follows that the 
temperature of the boiling point depends upon the 
atmospheric pressure. At an elevation high above 
the sea's level, as on a mountain, the pressure is less 
and the boiling point is lowered while in a steam 
boiler, where the pressure is increased, the boiling 
point is raised. The tension is measured in mil- 
limeters of mercury. 

52. Water of Crystallization. When the w iter 
is evaporated from the solution of a salt, the salt 
nearly always takes a crystalline form. In a great 
number of cases it is found that a certain definite 
number of molecules of water adhere to the salt. 
and that this water is necessary to the formation of 
the crystals ; for when the water is removed by 
heat, the crystals no longer retain their shape, but 
fall to powder. The water thus combined is called 
water of crystallization. 

The amount of this water varies considerably, 
ten or twelve molecules, or even more, being quite 
often found. The amount which a given com- 



LECTURE NOTES. 39 

pound requires may vary considerably with the 
temperature of crystallization, but for a given tem- 
perature it is invariable. 

The temperature at which crystals part with their 
water of crystallization is quite variable. Some lose 
their water on exposure to the air, the weter slowly 
evaporating and the salt falling to powder. This 
giving up of water at the ordinary temperature is 
called efflorescence . Some salts lose part of their 
water at ioo°, and require a higher temperature, 
often as high as 250 , before losing the rest. There 
are other salts which attract water so strongly, 
when exposed to the air, that they become partly 
or entirely liquified. This taking on of water is 
called deliquescence. Just what the relations are 
that exist between crystals, and their water of crys- 
allization, is not well known. 

53. Natural Waters. Since water dissolves so 
many substances, the natural waters are never en- 
tirely free from impurities. These impurities may 
consist in part of insoluble matter, held in suspen- 
sion by the water, and easily removable by filtra- 
tion. The soluble matter can only be removed by 
distillation, or treatment with chemicals. Rain 
water is the purest form of natural water, and this 
contains dust and soluble impurities washed from 
the atmosphere. Spring water always contains 
substances dissolved from the soil through which it 
flows. 

When water contains an insufficient quantity of 



40 LECTURE NOTES. 

dissolved matter to affect its taste, it is termed 
fresh water ; whereas, when it has a distinct taste, 
or possesses medicinal qualities, it is called mine- 
ral water. Those salts which are most often found 
in water, are carbonates and sulfates of calcium 
and magnesium, and different salts of sodium, po- 
tassium, and lithium. Salts of other elements, such 
as iron, and gases, particularly carbon dioxid. are 
often found. 

Waters are often spoken of as hard, or soft, ac- 
cording as they contain large or small quantities 
calcium or magnesium salts. The hardness of wa- 
ter is shown by its action upon soap, and deter- 
mined by the amount necessary to produce a per- 
manent lather in the water. Some salts may be re- 
moved from water by boiling. Such salts produce 
what is called temporary hardness, while those salts 
which cannot be removed by boiling produce per- 
manent hardness. 

Spring and river water, especially that which 
flows through wooded districts, contains more or 
less vegetable matter in solution. Such water is 
sometimes used for drinking, and while not to be 
recommended for such purposes, its use is attended 
with comparatively little harm. The water supply 
which comes from shallow wells, not infrequently 
contains more or less animal matter in solution. 
Such water should at once be condemned for drink- 
ing purposes, as it is certain evidence of sew 
contamination, and there is no longer any doubt 



LECTURE NOTES. 4 1 

that many epidemic diseases are contracted, and 
spread, by means of impure drinking water. 

Hydrogen dioxid. Molecular formula, H 2 2 . Molec- 
ular weight, 34. 

54. Occurrence and Preparation. This interest- 
ing compound exists in minute traces in the atmos- 
phere, and is produced in small quancities in some 
of the processes for the production of ozone. 

It is most commonly prepared by decomposing 
barium dioxid by means of dilute sulfuric acid, thus ; 

Ba0 2 + H 2 S0 4 = BaS0 4 + H 2 2 . 
The insoluble barium sulfate is allowed to settle; 
and the liquid filtered off and concentrated in a 
vacuum. 

55. Properties and Uses. Hydrogen dioxid is 
a thick, oily liquid. When pure it is colorless, but 
has a bitter taste. It is a very unstable compound, 
easily decomposing into oxygen and water, and is 
therefore a powerful oxidizing agent. A solution 
of this compound in water, is more stable, and, if 
kept at a low temperature, does not decompose rap- 
idly. It is used for bleaching organic substances, 
for restoring the colors of oil paintings, and for re- 
moving stains from old manuscripts and engravings. 
It is also being used quite extensively in analytical 
chemistry for the separation of certain metals. 

56. The Halogen Group. The four elements, 
fluorin, chlorin, bromin and iodin, constitute a 



42 LECTURE NOTES. 

group known as the "halogens,'" or salt producers. 
These elements differ considerably in their physi- 
cal properties, but are very much alike in their 
chemical properties, and possess powerful chemical 
affinities. They all combine with hydrogen to 
form the halogen acids, and with most of the me- 
tals, directly, to form salts. They are all univa- 
lent in their compounds with hydrogen, and with 
the metals, but in compounds with oxygen they 
exhibit a higher valence. The chemical affinity of 
these elements varies inversely as their atomic 
weight, fluorin having the strongest and iodin the 
weakest affinity of the four. Chlorin is the most 
common, and the typical element of the group. 

The compound radical cyanogen, (CN), acts 
much like the elements of this group. It forms 
compounds in every way analogous, and so is often 
classed as a member of the group. Its salts are 
called cyanids. 

Chlorin. Symbol, CI. Atomic weight, 35.4. 

57. History and Occurrence. Chlorin was first 
obtained in the free state by Scheele in 1774, who 
prepared it by the action of hydrochloric acid upon 
an ore of manganese. It was at first supposed to 
be an oxid of hydrochloric acid, and it was not un- 
til 1810, that Davy proved it to be an element, and 
gave it its name, chlorin. 

Chlorin never occurs free in nature, on account 
of its strong affinity for most of the metals. Its 



LECTURE NOTES. 43 

most important compound is sodium chlorid, or 
common sea-salt, which is found in large quantities 
in sea-water, in salt lakes, and in mineral springs. 
It is found as chlorids of magnesium, calcium, and 
potassium associated with sodium chlorid. The 
chlorids are also found in the earth forming vast 
deposits, like those at Stassfurt, in Germany, and 
about Syracuse, New York. 

58. Preparation. Chlorin is most conveniently 
prepared by the action of hydrochloric acid upon 
manganese dioxid, thus : 

4 HC1 + Mn0 2 = M11CI2 + 2 H 2 + Cl 2 . 
It can also be obtained from its most common com- 
pound, sodium chlorid, b} ? heating this with sul- 
furic acid and manganese dioxid, thus: 
2 NaCl -f 2 H 2 S0 4 + Mn0 2 = 

MnS0 4 + Na 2 S0 4 + 2 H 2 + Cl 2 . 

Almost any highly oxidized compound, if heated 
with hydrochloric acid, will yield chlorin. 

There are several processes for the mariufacture 
of chlorin on a large scale, the principle involved, 
being in all cases, similar to that in the equations 
just given. 

59. Properties. Chlorin is a gas, having a yel- 
lowish-green color, and a most disagreeable and 
suffocating odor, which, when present in very 
small quantities, resembles that of seaweed. 

It cannot be breathed, for, in small quantities, it 
is an irritant poison, producing coughing and inflam- 



44 LECTURE NOTES. 

mation of the mucous membrane, and, if inhaled in 
the pure state, may even cause death. It is about two 
and one-half times as heavy as the air, and a liter of 
the gas at normal temperature and pressure weighs 
3.17 grams. Under a pressure of six atmosphe 
o° it becomes a yellow liquid. It is quite soluble in 
water, one volume of which dissolves about 2.5 vol- 
umes of chlorin at the ordinary temperature. If a 
solution in water be exposed to sunlight, the water 
is decomposed, hydrochloric acid and oxygen being 
formed, thus : 

2 H,0 + 2 CI, = 4 HC1 + O,. 

Chlorin combines directly with all the common 
elements except oxygen, nitrogen, and carbon. 
Many of the metals combine with chlorin at the or- 
dinary temperature, giving light and heat, and 
forming a chlorid, while others require strong 
heating before combination takes place. 

It has a very strong affinity for hydrogen, as 
in its decomposition of water, and hence is a strong 
oxidizing agent. In the presence of water it de- 
stroys organic coloring matter and so is much used 
in the process called bleaching. 

60. Bleaching. A substance is said to be bleach- 
ed when its color is removed, so as to make it white, 
or light colored. Bleaching is a very important in- 
dustry in the arts, especially in the cotton and pa- 
per trade. Chlorin will bleach only in the pres- 
ence of water, hence the action is one of oxidation. 
the color being destroyed by the liberated oxygen. 



LECTURE NOTES. 45 

The excess of chlorin, and the hydrochloric acid, 
produced in the operation, is removed by the addi- 
tion of what is called an antichlor, and some weak 
alkali, like sodium carbonate. Chlorin will not 
usually bleach mineral colors, or those produced 
by carbon, so that printer's ink is not affected by 
this agent. 

This action of chlorin makes it valuable for the 
destruction of the poisonous germs of disease, and 
for removing the bad odors arising from the decay 
of organic matter. It is on this account much used 
as a disinfectant. 

COMPOUND OF CHLORIX WITH HYDROGEN. 

Hydrogen Chlorid, or Hydrochloric Acid. Molecular 
formula, HC1. Molecular weight, 36.4. Den- 
sity, 18.2. 

61. History and Occurrence. Hydrochloric acid 
was known to the Arabian alchemists under the 
name xi spirit of salt." It was known to most of 
the alchemists, in solution, and it was first prepar- 
ed as a gas, and collected over mercury, by Priest- 
ley, who called it marine-acid air. It was suppos- 
ed to be a compound of oxygen until 18 10, when 
its true composition was determined by Davy. 

It occurs in the gases from active volcanoes, and 
in the water of certain rivers which flow through 
volcanic districts. Its salts are called chlorids, and 
occur as given under chlorin. 



46 LECTURE NOTES. 

62. Preparation. The common way to prepare 
hydrochloric acid, is by acting upon some chlorid 
with sulfuric acid. Sodium chlorid is usually em- 
ployed, and the following equation represents the 
action : 

2 NaCl + H2SO4 = Na,S0 4 + 2 HC1. 
Hydrochloric acid may also be prepared, by the 
direct union of its elements, that is, by synthesis. 
Hydrogen and chlorin will combine by heat, by the 
electric spark, or by the action of sunlight at the 
ordinary temperature, the union taking place with 
explosive violence. Commercial hydrochloric acid 
is obtained in enormous quantities, as a by-product 
in the manufacture of sodium carbonate, by the Le- 
blanc process. 

63. Properties. Hydrochloric acid is a col< 
gas, having a pungent, suffocating odor, and a sour 
taste. Under strong pressure, at a low temperature, 
it condenses to a colorless liquid. It is a little heav- 
ier than air, its specific gravity being 1.27. It does 
not burn nor does it support combustion. It fumes 
strongly in ordinary air, owing to its union with 
atmospheric moisture. It is very soluble in water, 
one volume of which dissolves about 500 volumes 
of the gas, at o°, and about 450 volumes at the or- 
dinary temperature. 

This solution is the form in which hydrochloric 
acid is ordinarily used, in the laboratory, and in 
the arts, and is known, commercially, as muriatic 
acid. 



LECTURE NOTES. 47 

This aqueous solution contains, when saturated, 
about 42 per cent, of hydrochloric acid, and has a 
specific gravit3 T of 1.21. When such a solution is 
heated, the gas is given off until the strength has 
been reduced to about 20 per cent., and the specific 
gravity to 1.10, when it boils without further 
change. 

COMPOUNDS OF CHLORIN WITH OXYGEN AND 
HYDROGEN. 

64. The Oxids of Chlorin. Chlorin forms three 
oxids, 

Chlorin monoxid, CI2O, 
Chlorin trioxid, CI2O3, and 
Chlorin peroxid, CIO2. 
All of these compounds are gases, at the ordinary 
temperature. They are very unstable, and a very 
slight elevation of temperature causes them to ex- 
plode with considerable violence. Only the per- 
oxid has any practical value. 

65. Chlorin peroxid. This compound is formed 
when a chlorate is decomposed by sulfuric acid, at 
a little above the ordinary temperature. Potassium 
chlorate is usually employed for this purpose, and 
the reaction is as follows : 

3 KClOs + 3 H2SO4 = 

3 KHSO4 + HCIO4 + H,0 + 2 CIO2. 

Chlorin peroxid is a heavy yellew gas, having a 

peculiar odor, a little like that of chlorin and burnt 



48 LECTURE NOTES. 

sugar. Iii the cold, it easily condenses to a dark 
red liquid, and it is very explosive, in both th< 
eous and liquid form. 

It is a powerful oxidizing agent, and many sub- 
stances take fire when brought into contact with it. 
It is quite soluble in water forming a yellow solu- 
tion. 

66. The Oxy-acids of Chlorin. There are four 
oxy-acids of chlorin. These are, 

Hypochlorous acid, HCIO, 

Chlorous acid, HC10,>, 

Chloric acid, HCIO::. and 

Perchloric acid, HC10 4 . 
These acids are all unstable, and only exist 
in aqueous solutions, They form salts which are 
not so easily decomposed, and some of them are 
very important commercial compounds. The acids, 
themselves, are all powerful oxidizing agents, which 
constitutes their principal use. 

67. Hypochlorous acid and its salts. This acid 
is only found in dilute solutions. It is valuable as 
a bleaching agent, but since its salts act in a simi- 
lar way they are more commonly employed. If 
chlorin gas is brought into contact with a base it 
forms, in part, a hypochlorite of the metal. The 
base usually employed is calcium hydroxid, or 
slaked lime, Ca(OH)j. This action produces 
bleaching powder \ commercially known aschlorid of 
li])u\ the equation for tins action is as foil... 

Ca(OH) 2 -f Cla = CaOCla 4 H,i v 



LECTURE NOTES. 49 

Bleaching powder may therefore be regarded as 
a mixture of calcium chlorid, CaCl 2 , add calcium 
hypochlorite, Ca(C10) 2 , and may be written, 

^ a \ o— CI. 
It is a white porous solid, having an odor like chlo- 
rin. It slowly decomposes in the air, or in an aque- 
ous solution, setting free hypochlorous acid, aud is, 
therefore, much used in bleaching, and as a disin- 
fectant. 

68. Chloric acid and its salts. This is the most 
important of the chlorin oxy-acids. It can be pre- 
pared by decomposing barium chlorate with dilute 
sulfuric acid, thus : 

Ba(C10 3 )2 + H2SO4 = BaS0 4 + 2 HCIO.3. 

Chloric acid is not very stable, and cannot be ob- 
tained stronger than 40 per cent., in an aqueous so- 
lution. It is a strong oxidizing agent, organic sub- 
stances being frequently oxidized so rapidly as to 
take fire. 

The most important salt of this acid, is potas- 
sium chlorate. This is prepared by leading chlo- 
rin into a solution of potassium hydroxid, thus : 

3 Cl 2 + 6 KOH = 5 KC1 + 3 H 2 + KCIO3. 

This compound is very much used in the labora- 
tory as an oxidizing agent, and in medicine, for 
treating certain diseases of the throat. 

69. Perchloric Acid. This acid is the most sta- 
ble of all this series of acids, and can be obtained 



50 LECTURE NOTES. 

pure, by treating potassium perchlorate with con- 
centrated sulfuric acid. When pure, it is a color- 
less liquid, and takes moisture rapidly from the air. 
It oxidizes organic substances so vigorously as to 
often cause explosion. 

Its salts, which are called perchlorates are not of 
special importance. 

Bromin. Symbol, Br. Atomic Weight, 79.9. 

70. History and Occurrence. Bromin was dis- 
covered in sea-water by Balard, in 1826. It never 
occurs free in nature on account of its strong affini- 
ties. It is usually found in connection with com- 
pounds of chlorin, as bromids of sodium, potassium 
or magnesium, in sea-water, in mineral springs, 
and in salt deposits, such as the one at Stassfurt, 
in Germany. 

71. Preparation. Bromin is prepared from bro- 
mids, by the same method employed tor the prepa- 
ration of chlorin, thus: 

2 NaBr + Mn0 2 + 2 H2SO4 = 

M11SO4 + Na,>S0 4 + 2 H 2 
It may also be prepared from the bromids by 
treating them with free chlorin, when the bromin 
is replaced by the chlorin, thus : 

2 NaBr + CI, = 2 NaCl -f Br.. 
It can be prepared in other ways, analogous to 
those employed for making chlorin. 

72. Properties. Bromin is a heavy, red liquid. 



LECTURE NOTES. 5 1 

which is so dark as to be opaque except in thin lay- 
ers. It is the only element, except mercury, which 
is a liquid at the ordinary temperature. Its specific 
gravity is 3.18; it evaporates quickly in the air at 
the ordinary temperature, and boils at 63 . It is 
somewhat soluble in water, 100 parts of which dis- 
solve a little more than three parts of bromin. This 
solution, known as bromin water, is much used as 
an oxidizing agent. It has a very disagreeable 
odor, and its vapor attacks the eyes, and causes 
great irritation when breathed. It is an irritant 
poison, and causes corrosive sores if dropped on 
the skin. 

Bromin very closely resembles chlorin in its 
chemical properties, but its affinities are weaker. 
It combines with most of the elements directly and 
with some of them, particularly potassium, with 
explosive violence. It may be used for bleaching 
the same as chlorin. 

Hydrobromic acid. Molecular formula, HBr. Mo- 
lecular Weight, 80 9. Density, 40.45. 

73. Preparation and Properties. Bromin forms 
only one compound with hydrogen, and that is hy- 
drobromic acid. The two elements can be made to 
combine directly, by heat, but do not combine in 
sunlight, as is the case in the corresponding com- 
pound of chlorin. 

It cannot be prepared from bromids bv means of 



52 LECTURE NOTES. 

sulfuric acid, being decomposed by the strong acid 
giving free bromin. 

It is best prepared by bringing together bromin 
and phosphorus in the presence of water. The re- 
action, which is quite violent and gives hydrobro- 
mic and phosphorous acids, is represented by the 
following equation : 

P + 3 Br + 3 H 2 = H 8 POa + 3 HBr. 

Hydrobromic acid is a colorless gas, fuming in 
moist air, and very soluble in water. This solution 
is the form in which it is generally used, and when 
saturated, has a specific gravity of 1.78. Its salts 
are called bromids. 

74. The Oxy-acids of Bromin. Bromin forms 
no compound with oxygen alone, but there are two 
and possibly three oxy-acids. These are, 

Hypobromous acid, HBrO. 

Bromic acid, HBrO;3, and, possibly. 

Perbromic acid, HBrO-i. 
They are named from their analogous chlorin 
compounds, and there is none to correspond to 
chlorous acid. The acids are in every way similar 
to the corresponding oxy-acids of chlorin. 

Iodin. Symbol, I. Atomic Weight, 126.8. 

75. History and Occurrence. Before the present 
method for making sodium carbonate was known. 
this important salt was obtained from sea-plants, 
by first burning them, and then extracting the salt 



LECTURE NOTES. 53 

by leaching the ash, which was called kelp or varec. 
In 1812, Courtois, while examining the mother-li- 
quor which remains after the sodium salts have 
crytallized, discovered iodin. 

Iodin does not occur free in nature, but, in small 
quantities, is very widely distributed in both or- 
ganic and inorganic compounds. It is found in 
sea-water and mineral springs, and especially in 
deep-sea-weed and in certain sea animals such as 
sponges and oysters. 

76. Preparation. The ash of the sea-weed is 
leached, the soda crystallized out, and the mother- 
liqucr treated with sulfuric acid, and manganese 
dioxid. The iodin, which is present in the form 
ofiodids, is thus liberated in the same manner as 
is chlorin and bromin, the reaction bemg as fol- 
lows : 

2 Nal + 2 H 2 S0 4 + M11O2 = 

MnSOi + Na 2 S0 4 + H,0 + I,. 
It may also be obtained from iodids, by treating 
them with chlorin or bromin, thus: 

2 Nal + Cl 2 = 2 NaCl + I 2 . 

77. Properties. Iodin is a dark gray crystal- 
line-solid, with an odor like very weak chlorin, and 
a sharp sour taste. It is quite heavy, its specific 
gravity being 4.95. It melts at 114 , and boils at 
184 , giving rise to a vapor which has a splendid 
deep blue color, when pure, but is violet when 
mixed with air. It is the heaviest vapor known, 
its specfic gravity being 8.72. 



54 LECTUkh NOTES. 

It is only very slightly soluble in water, but is 
easily soluble in water containing iodids in solu- 
tion, as well as in alcohol and ether. It destroys 
the skin and is used in medicine for cauterizing 
wounds, and as an irritant. lodin may be I 
nized by the blue color which it imparts to starch- 
paste, and which is very characteristic. Its com- 
pounds are used in medicine and in photography. 

Hydriodic acid. Molecular formula, HI. Molec- 
ular Weight, 127.8. Density, 63.0- 

78. Preparation and Properties. Hydriodi 

is prepared in a way similar to that for preparing 
hydrobromic acid, by allowing iodin and phospho- 
rus to act upon each other in the presence of water, 
thus : 

P+ 3 1+3 h,() = HsPOa +■ 3 HI 
Hydriodic acid is a gas, fuming strongly in the 
air. It is very soluble in water, but the solution 
is easily oxidized, in the presence of air, with libe- 
ration of iodin. At 1S0 the gas decomposes into 
hydrogen and iodin. 

79. The Oxids and Oxy-acids of Iodin. Iodin 
form only one oxid. called iodin pentoxid, 1 

There are two oxy-acids known, 

Iodic acid, HIOj and 
Periodic acid, II I< h> 

Iodic acid is the only comp >und of any impor- 
tance. It may be prepared by oxidizing iodin 



LECTURE NOTES. 55 

with concentrated nitric acid. It is a white crys- 
talline solid, and forms salts called iodates. 

Fluorin. Symbol, F. Atomic Weight, 19. 

80. History and Occurrence. It has long been 
known that if the mineral fluorite is heated with 
sulfuric acid, a compound is obtained which will 
etch glass. All attempts to isolate fluorin, even in 
a comparatively pure state, have failed until very 
recently. In 1886 Moissan succeeded in obtaining 
the pure element, and in studying its properties. 

Fluorin occurs, combined with calcium as cal- 
cium fluorid, CaF 2 . in the mineral fluorite, or fluor- 
spar ; combined as a double fluorid of sodium and 
aluminum, AlF3,3NaF, in the mineral cryolite ; 
in small quantities in man} 7 other mineral sub- 
stances; in minute traces in the bones and teeth of 
animals, in blood and in milk. 

81. Preparation and Properties. Fluorin was 
obtained by Moissan, by decomposing perfectly an- 
hydrous hydrofluoric acid at a very low tempera- 
ture, by means of the electric current, fluorin ap- 
pearing at the positive pole. 

Obtained in this way, fluorin is a colorless gas, 
having the most powerful affinities of any known 
element. It decomposes water with great vigor, 
giving ozone and oxygen. Many elements take 
fire in it spontaneously. It combines with hydro- 
gen in the cold and in the dark, and liberates chlo- 



56 LECTURE NOTES. 

rin from its compounds. It does not combine with 
oxygen in any form, being the only element which 
does not do so. 

Hydrofluoric acid. Molecular formula. HF. Mo- 
lecular Weight, 20. Density, 10. 

82. Preparation and Properties. Hydrofluoric 
acid may be prepared by the action of sulfuric acid 
upon any fluorid. We usually employ powdered 
fluorite, that is, calcium fluorid, the action being 
represented by the following equation : 

CaF 2 + H 2 S04 = CaS0 4 + 2 HF. 

Pure hydrofluoric acid is a colorless and ven 
volatile liquid, which fumes strongly in the air. 
It boils at 19 , and, when in the gaseous state, does 
not again condense to a liquid until cooled to o°. 
The anhydrous acid is a powerful caustic, destroy- 
ing the skin, and causing painful ulcers which are 
difficult to heal. It is easily soluble in water, and 
is usually employed in this form, being preserved 
in bottles of gutta percha, or platinum. The mole- 
cule at a low temperature is found to be HF,, and, 
in this case, the fluorin atom is therefore trivalent. 
the graphic formula for hydrofluoric acid being 
thus, 

H— F=F— H. 

Its most remarkable property is that of etching 
glass. Glass is composed, principally, <>t" silicon 
dioxid, and the etching is caused by the affinity of 



LECTURE NOTES. 57 

fluorin for silicon, and the formation of gaseous 
silicon fluorid, the action being as follows : 
S1O2 + 4 HF = SiF 4 + 2 H 2 0. 
Either the gas, or the solution in water may be 
used for etching. The glass is prepared by first 
covering it with wax, and then removing the wax 
in the pattern to be etched. The glass is then ex- 
posed to the gas, or the solution applied with a 
brush. The salts of hydrofluoric acid are called 
fluorids. 

83. The Sulfur Group. The elements sulfur, 
selenium, and tellurium, form what is know as the 
sulfur group. They differ considerably in their 
physical properties, but chemically are much alike, 
forming compounds in every way analogous. Sul- 
fur is a very common element while selenium and 
tellurium are quite rare. In compounds with the 
metals and with hydrogen, these elements are biva- 
lent and very much resemble oxygen. They form 
compounds with oxygen, however, and in them ex- 
hibit great variation in valence, being hexads in 
some of them. They all exhibit a marked negative 
character. This decreases as their atomic weights 
increase, sulfur having the strongest affinities and 
being the type of the group. 

Sulfur. Symbol, S. Atomic Weight, 32. 

84. History and Occurrence. Sulfur has been 
known since the very earliest times. It was verv 



58 LECTURE NOTES. 

highly regarded by the alchemists, and believed by 
them to be the principle of combustibility. 

Sulfur is a very widely distributed element, and 
occurs both free and combined with other elements. 
Free sulphur is found in volcanic districts, particu- 
larly in Sicily, where it is probably formed by the 
decomposition of certain volcanic gases. 

The compounds of sulfur with the metals are 
very numerous, and occur in all parts of the world. 
The principal ones are pyrite, or iron pyrites, FeS-2; 
galenite, PbS ; sphalerite, ZnS ; cinnabar, HgS. 
Another important compound of sulfur is calcium 
sulfate, or gypsum, CaSO-t. 

Sulfur is an important constituent in many or- 
ganic compounds, and comprises about one per 
cent, of all albuminous substances; and it is to the 
presence of sulfur, that the disagreeable odors of 
decaying animal matter are largely due. 

85. Preparation. Most of the sulfur of com- 
merce is obtained from the native material. This 
is usually found mixed with marl, gypsum, and 
other earthy impurities. To free it from these, the 
early method was to place heaps of the impure Mil- 
fur in holes dug in the ground, and set them on fire 
in the evening. The heat of the sulfur burning on 
the surface, melted the rest of it. which ran to the 
bottom, and was removed in the morning, fairly 
free from the impurities. A somewhat more eco- 
nomical plan is now employed, but the principle is 
the same. 



LECTURE NOTES. 59 

The crude sulfur, thus obtained, is afterwards 
purified by distillation, the vapor being led into a 
cold chamber, where it condenses, forming- the so- 
called flowers of sulfur ; or, the melted sulfur is cast 
in wooden moulds in the form which we call roll sul- 
fur, or brimstone . 

Sulfur may be prepared by heating certain sul- 
fids, such as pyrite, the action being as follows : 
3 FeS 2 = Fe 8 S 4 + S 2 . 

A very interesting method for preparing it is the 
way in which it is probably formed in nature. This 
is»by the action of sulfur dioxid upon hydrogen sul- 
fid. both of which gases are found issuing from all 
active volcanoes. This action is as follows : 
S0 2 + 2 H 2 S = 2 H 2 + 3 S. 

86. Properties. Ordinary sulfur is a yellow, 
brittle solid, and has a slight odor, when rubbed. 
When heated to 260 in the air, sulfur, takes fire 
and burns with a pale blue flame, giving off a char- 
acteristic, suffocating odor. It supports the com- 
bustion of many metals exhibiting thus its likeness 
to oxygen. It is insoluble in water, but dissolves 
in carbon disulfid, and in certain organic com- 
pounds. 

Sulfur melts at 114 , forming a thin amber color- 
ed liquid. Upon further heating, this becomes 
dark and thick, until at about 260 it is almost sol- 
id, and very dark. Above 300 it again becomes 
thin, and at 448 it boils, giving off a dark red 
vapor. 



6o LECTURE NOTES. 

At 500 its density is found to be 96, which 
shows that its molecule at that temperature con- 
tains six atoms. Above this temperature the mol- 
ecule begins to dissociate and at 1000 its density 
becomes 32, showing that the molecule at that 
temperature contains but two atoms. Its com- 
pounds with the metals are called sulfids. 

87. The Allotropic forms of Sulfur. Sulfur is 
capable of existing in three allotropic forms, due, 
without doubt, to changes in the number of atoms 
in the molecule. 

The first variety is known as rhombic or octohed- 
ral sulfur, and is the form in which it occurs in na- 
ture, and which is obtained by allowing sulfur to 
crystallize from a solution. It is a lemon-yellow, 
crystalline solid, with a specific gravity of 2.05, 
and is easily soluble in carbon disulfied. 

Tne second variety is called monoclinic <>r pris- 
matic sulfur ■, and is obtained when melted sulfur is 
allowed to cool quickly. In order to prepare this, 
sulfur is melted in a crucible, and allowed t<> cool. 
As scon as a crust is formid on the surface, t his is 
broken and the portion which is still liquid poured 
out, when the solidified portion is seen to c<>n>i>t 
of long, transparent, brownish -yellow needles. 
This varity melts at 120 , ha^ a specific gravity of 
1.98, and gradually becomes lighter in color, and 
changes to the rhombic modification. 

The third variety is called plastic or amorphous 
sulfur, and is obtained when sulfur, heated to 



LECTURE NOTES. 6l 

or more, is suddenly cooled by pouring it into wa- 
ter. It is a dark brown, tenacious mass, like rub- 
ber, is only partially soluble in carbon disulfid, and 
has a specific gravity of 1.95. It hardens slowly at 
the ordinary temperature, and changes into the 
first variety. This change takes place suddenly at 
about ioo° evolving considerable heat. 

An amorphous form of sulfur is produced when 
certain sulfids are acted upon by hydrochloric acid. 
This is known as milk of sulfur or lac sulfur, is sol- 
uble in carbon disulfid, and gradually changes to 
the first variety. 

COMPOUNDS OF SULFUR WITH HYDROGEN. 

Sulfur forms two compounds with hydrogen, 
Hydrogen sulfid, H2S, and 
Hydrogen persulfid, H2S2. 

Hydrogen Sulfid. Molecular formula, BUS. Molec- 
ular Weight, 34. 

88. History and Occurrence. Although certain 
processes were known to the alchemists, during 
which hydrogen sulfid must have been formed, it 
does not seem to have been recognized until 1777, 
when Scheele discovered it, by heating sulfur in 
hydrogen gas. 

Hydrogen sulfid occurs in nature in volcanic gas- 
es and in certain natural waters, the so-called sul- 



62 LECTURE NOTES. 



fur springs. It is also formed in nature by the de- 
cay of organic matter containing sulfur. 

89. Preparation. Hydrogen sulfid is easily ob- 
tained by the action of an acid upon some sulfid. 
Ferrous sulfid and sulfuric acid are usually employ- 
ed, the action taking place in the cold according to 
the following equation : 

FeS 4 H2SO4 = FeSC4 + H 2 S. 
If required pure, antimony sulfid and hydrochlo- 
ric acid are used, thus : 

Sb 2 S 3 -J- 6 HC1 = 2 SbCla - 3 H,S. 
It may be obtained by direct union of the ele- 
ments, by leading hydrogen gas through boiling 
sulfur; also by the reduction of certain sulfids by 
means of hydrogen. 

90. Properties and Uses. Hydrogen sulfid is a 
colorless gas, having a sweetish taste, and a very 
disagreeable odor, quite similar to that of rotten 
eggs. It is an active poison, less than one per 
cent, in the atmosphere being dangerous to breathe. 
It is an inflammable gas, and burns with a pale blue 
flame. If two volumes of the gas are mixed with 
three of oxygen it explodes with considerable vio- 
lence. It is soluble in water, one volume of which 
dissolves about three volumes of the gas at the or- 
dinary temperature. This solution p assesses weak 
acid properties and is sometimes called hydrosulfu- 
ric acid. The sulfids are regar led as s tits M this 
acid. The gas decomposes easily in this solution 



LECTURE NOTES. 63 

forming water, and depositing sulfur. The halogen 
elements decompose it easily, and so dilute chlorin 
is used as an antidote for poisoning with this sub- 
stance. 

It is one of the most useful reagents in the labo- 
ratory since it forms insoluble sulfids with a num- 
ber of the metals, and so is used to percipitate 
them from their solutions. It also acts as a reduc- 
ing agent, and is often used for this purpose. 

91. Hydrogen persulfid, H 2 S 5 - This compound 
is formed by decomposing potassium or calcium 
persulfid, with hydrochloric acid. It is a heavy, 
oily liquid, decomposing easily into hydrogen sul- 
fid and sulfur, and has no particular value, save as 
it shows the similarity of sulfur and oxygen, it be- 
ing analogous to hydrogen dioxid. 

92. The Halogen compounds of Sulfur. There 
are three compounds of sulfur with chlorin, each 
formed by direct union of the elements. These are, 

Sulfur monochlorid, S2CI2, 
Sulfur dichlorid, SC1 2 , and 
Sulfur tetrachlorid, SC1 4 . 
The monochlorid is formed by leading dry chlo- 
rin into melted sulfur at the ordinary temperature. 
It is a yellow liquid, dissolves sulfur readily, and 
is principally used for this purpose, and for vulcan r 
izing rubber. 

The dichlorid is formed by leading chlorin into 
the monochlorid at o°, and the tetrachlorid, by 
leading chlorin into the dichlorid at — 22 . 



64 LECTURE NOTES. 

Sulfur forms one bromid, S^Br-i, and one iodid, 
S2I2, each by direct union of the elements. 

No compound of sulfur with fluorin is known. 

COMPOUNDS OF SULFUR WITH OXYGEN. 

There are several compounds of sulfur with oxy- 
gen, but only two are of any importance. These 
are, 

Sulfur dioxid, SO2, and 

Sulfur trioxid, SO3. 

Sulfur dioxid. Molecular formula, S0_>. Molecular 
Weight, 64. 

93. Occurrence and Preparation. Sulfur dioxid 
is found in nature in volcanic gases, and is readilv 
produced by burning sulfur in the air, or in oxy 
gen. 

It is most conveniently prepared in the laborato- 
ry, by the action of hot concentrated sulfuric acid 
on certain elements, like copper, the action being 
as follows : 

Cu + 2 H2SO4 = CuS0 4 + 2 H.O 4- SO>. 

It is probable that the action is first to produce 
hydrogen, which, in the nascent state, and at the 
high temperature, decomposes the sulfuric acid. 

94. Properties. Sulfur dioxid is a colorless 
having a peculiar suffocating odor like a burning 
sulfur match. It is not combustible, neither is it a 



EECTURE NOTES. 65 

supporter of combustion. It is quite easily soluble 
in water, one volume of which, at the ordinary 
temperature, dissolves about 50 volumes of the gas. 
There is probably a weak chemical union in this 
solution, forming sulfurous acid, thus : 
S0 2 + H 2 = H2SO3. 

Sulfur dioxid is easily condensed to a colorless, 
mobile liquid, by a pressure of about three atmos- 
pheres, or a temperature of — io°. When this 
liquid is evaporated, a great amount of heat is ren- 
dered latent, thus producing great cold. If a 
stream of air is driven through the liquid the tem- 
perature sinks to — 50 

It is much used in the laboratory as a reducing 
agent, and in the arts as a bleaching agent and dis- 
infectant. 

Sulfur Trioxid. Molecular formula, S0 3 . Molecu- 
lar weight, 80. 

95. Preparation and Properties. This substance 
can be formed by heating the compound known as 
pyrosulfuric acid, the equation being as follows : 
H2S2O7 === H2SO4 + S0 3 . 

It can also be formed synthetically by leading 
sulfur dioxid and oxygen over heated platinum 
sponge, or platinized asbestos. 

Sulfur trioxid is a white crystalline solid, which 
melts at 16 , and boils at 46 . It dissolves in water 



66 LECTURE NOTES. 

with a hissing sound, forming sulfuric acid, and 
giving off a great amount of heat. It gives dense 
white fumes when exposed to the air, owing to the 
absorption of moisture. At a red heat it is decom- 
posed into sulfur dioxid and oxygen. 

COMPOUNDS OF SULFUR WITH OXYGEN AND HYDRO- 
GEN. 

96. The Oxy-acids of Sulfur. There are no less 
than nine oxy-acids of sulfur. These are : 

Hyposulfurous acid, HgSOs, 
Sulfurous acid, H2SO3, 
Sulfuric acid, H>S0 4 , 
Pyrosulfuric acid, H2S9O7, 
Thiosulfuric acid, HgSjOg, 
Dithionic acid, Hs&Oe, 
Trithionic acid, H2S3O6, 
Tetrathionic acid, H9S4O6, and 
Pentathionic acid, H2S5O6. 
Most of these acids are rare, and exist only in 
their salts, but a few of them are very important. 

97. Sulfurous Acid, ILSOs. This is a weak, un- 
stable acid, which is probably formed when sulfur 
dioxid is dissolved in water. (See Art. 94, It 
is known only in aqueous solution. It smells like- 
sulfur dioxid, and has a strong acid reaction. It is 
a dibasic acid, and its salts, which arc called sul- 
fites, and are quite important, may be formed by 
saturating solutions of bases with sulfur dioxid. It 



LECTURE NOTES. 67 

is used in the laboratory for the same purposes as 
sulfur dioxid. 

Sulfuric Acid. Molecular formula, H 2 S0 4 . Molec- 
ular weight, 98. 

98. History and Occurrence. Sulfuric acid was 
probably known to the Arabian alchemists in an 
impure state. A process for preparing it was first 
described by Basil Valentine, in the 15th century. 
The present method of manufacture was proposed 
by Dr. Roebuck in 1770. 

Sulfuric acid occurs free in the waters of certain 
rivers, and mineral springs. It is found also in the 
saliva of certain mollusks. Its salts, the sul- 
fates, are found in all parts of the world, forming 
the minerals gypsum, CaSCU, barite, BaSOi, and 
many others. 

99. Preparation. Sulfuric acid can be formed 
by adding water to sulfur trioxid, also by the oxi- 
dation of sulfur, or sulfur dioxid, by means of nitric 
acid. The latter is the method employed for its 
manufacture on a large scale. Sulfur dioxid is 
formed, either by burning sulfur in the air, or by 
roasting certain sulfur ores in a suitable furnace. 
Nitric acid and steam are then brought into con- 
tact with the sulfur dioxid and air, when the fol- 
lowing action takes place : 

3 S0 2 + 2 HNO3 + 2 H,0 = 3 H2SO4 -f 2 NO. 



68 LECTURE NOTES. 

The nitric oxid, NO, formed in this action, is 
then acted upon by the air forming nitric peroxid, 
thus : 

2 NO + 2 = 2 X< h 

The nitric peroxid is then capable of oxidizing 
more sulfur dioxid, and does so as follows : 
S0 2 + NO2 + H2O = H2SO4 -f NO. 

Sulfur dioxid will not oxidize rapidly in the 
presence of air and water alone, but does so in the 
presence of the higher oxids of nitrogen. The nitric 
oxid acts thus as a carrier, between the oxygen of 
the air and the sulfur dioxid. 

100. Manufacture. The manufacture of sul- 
furic acid is such a very important industry that it 
deserves more than a passing mention. All of the 
sulfuric acid of commerce is now 7 made by the leaden 
chamber process, the principle involved being the 
one already stated in the previous article. 

This process, which is a continuous one. consists 
in bringing the different substances together in 
a series of large chambers lined with lead. The 
sulfur dioxid is usually obtained by roasting pyrite, 
and the nitric acid from sodium nitrate, known com- 
mercially as Chili saltpeter. The air is brought in 
with the sulfur dioxid, and the steam is conducted 
into different parts of the chambers. 

Theoretically, only a very small quantity oi 
nitric acid is necessary to oxidize a large amount of 
sulfur dioxid, since the nitric oxid. which is 



LECTURE NOTES. 69 

formed, is oxidized in the presence of air, forming 
nitric peroxid, which can oxidize more sulfur diox- 
id, forming again nitric oxid, when the above pro- 
cess is repeated. This would be true were it not for 
the large amount of nitrogen in the air, which so 
dilutes the gases that they would soon become inac- 
tive. To avoid this, and also to avoid wasting the 
oxids of nitrogen, the gases are forced to pass on, 
and after leaving the chambers, pass into what is 
called a Gay-Lussac tower. This is a tall tower, 
lined with lead, and filled with coke, over which 
strong sulfuric acid is made to run. The nitrogen 
oxids are absorbed by this, with formation of nitro- 
sulfonic acid, NO2HSO3, known as chamber acid 
crystals, while the nitrogen passes on and escapes 
through a chimney. 

This nitrosulfonic acid, with the excess of sul- 
furic acid, is conducted back into what is called a 
Glover tower, where it meets the gases, hot from the 
sulfur furnaces, and is decomposed. The gases 
then pass into the leaden chambers to go through 
the same process again, the unchanged sulfuric 
acid passing to a proper receptacle at the bottom. 

The acid, as it comes from the leaden chambers, 
is diluted with water, and contains only about 60 
per cent, of pure acid. It is then concentrated in 
leaden pans until it acquires a strength of about 78 
per cent. At this strength it begins to attack the 
lead, and the concentration is therefore continued 
in vessels of platinum or glass, until it reaches 



70 LECTURE NOTES. 

about 98 per cent., which is the strength usually 
found in the concentrated acid. 

101. Properties and Uses. Sulfuric acid, when 
pure, is a colorless, odorless, oily liquid. It has a 
specific gravity of 1.84. When heated, it begins to 
fume and partially decompose at 30 , and boils at 
338 . At a little above 400 it is entirely decom- 
posed into sulfur trioxid and water, as shown by the 
density of its vapor, which is found to be only 24.5 
at this temperature. These two substances com- 
bine again on cooling. 

The concentrated acid has a very strong attrac- 
tion for water, the union of the two being attended 
with the evolution of a great amount of heat and a 
contraction of volume. In mixing the two, the 
acid should always be poured into the water, and 
never the reverse. 

Concentrated sulfuric acid does not act upon 
many of the metals when cold, but does in some 
cases when heated, in which case sulfur dioxid is 
formed. (See Art. 93.) The dilute acid acts 
upon the more positive metals, with evolution of 
hydrogen, and the formation of sulfates. Many 
organic substances are decomposed by sulfuric acid, 
which takes from them the elements of water, set- 
ting free carbon. This explains the charring of 
wood, paper, sugar, etc., when acted upon by this 
acid. Nearly all salts are decomposed by it, giv- 
ing the acids from which the salts were derived. 
The attraction which sulfuric acid has for water is 



LECTURE NOTES. 7 1 

utilized in the laboratory for the purpose of desic- 
cating, or drying gases. 

Next to water, it is the most important compound 
known to the chemist, and there is hardly an arti- 
cle manufactured, or a chemical process known, 
which does not, directly or indirectly, employ sul- 
furic acid. 

102. Pyrosulfuric Acid, H9S2O7. This is also 
known as fuming or Nordhausen sulfuric acid, be- 
cause formerly manufactured at Nordhausen, in the 
Hartz Mts., and may be regarded as a solution of 
sulfur trioxid in sulfuric acid. It is also called 
disulfuric acid, since it may also be regarded as 
derived from tw T o molecules of sulfuric acid, by the 
removal of one molecule of water. 

It may be prepared by dissolving sulfur trioxid 
in sulfuric acid, and is a thick, brown, oily liquid, 
which, when cooled, forms crystals, melting at 35 . 
It fumes strongly in the air, owing to the escape of 
the volatile sulfur trioxid. It is a dibasic acid, 
forming a well defined class of salts, and is used for 
dissolving indigo, and in the manufacture of 
alizarine. 

103. Thiosulfuric Acid, H2S2O3. This acid is 
not known in the free state, but its salts are very 
important bodies. They are best prepared by heat- 
ing sulfites with sulfur, thus : 

Na 2 S0 3 + S = Na 2 S-20 3 . 
This acid is known commercially as hyposulfu- 
rous acid, and its salts as hyposulfites. The thio- 



72 LECTURE NOTES. 

sulfates (or hyposulfites) are solvents for many in- 
soluble compounds, such as the halogen salts of 
silver, and hence they are much used in photogra- 
phy. Sodium thiosulfate is also used as an anti- 
chlor in chlorin bleaching. (See Art. 60.) 

Selenium. Symbol, Se. Atomic weight, 79. 

• 104. History and Properties. Selenium was 
discovered by Berzelius in 1817, in the deposits 
from the leaden chambers of a sulfuric acid fac- 
tory in Sweden. It is a rare element, and 
occurs occasionally free, but generally combined, 
as selenid of copper, lead, or silver. It is mostly 
obtained from the sulfuric acid residues. It exists 
in two allotropic forms, one of which is a dark, red- 
dish-brown, crystalline solid, having a specific 
gravity of 4.5, and soluble in carbon disulfid ; 
while the other is a dark gray solid, with a specific 
gravity of 4.8, and insoluble in carbon disulfid. It 
melts at 217 and boils at about 700 . It burns 
with a blue flame, forming the oxid, Se(\>, which 
has an exceedingly disagreeable odor. It unites 
with the metals, directly, to form selenids, and 
forms compounds analogous to those of sulfur. 

Tellurium. Symbol, Te. Atomic weight, 125. 

105. History and Properties. Tellurium was 
discovered by Klaproth, in 1798, in a gold ore 



LECTURE NOTES. 73 

from Transylvania. It is a very rare element, 
and occurs occasionally free, but generally as 
tellurid of gold, silver or bismuth. It is a tin- 
white solid, quite brittle, and a good conductor 
of heat and electricity. Its specific gravity is 6.25, 
and it is quite metallic in its physical properties. 
It melts at about 500 , and burns in the air with a 
blue flame forming the oxid TeO-2. It is insoluble 
in carbon disulfid. It is an unimportant element, 
forming compounds analogous to those of sulfur 
and selenium. 

106. The Nitrogen Group. The elements of this 
group are nitrogen, phosphorus, arsenic, antimony, 
bismuth, and some rare elements. They differ very 
much physically, and to a considerable extent 
chemically. Nitrogen is a gas, and is one of the 
least active of all the elements. All the others are 
solids, and phosphorus is one of the most active of 
elements, while antimony and bismuth are usually 
classed among the metals, the latter exhibiting 
marked metallic properties. They all form com- 
pounds with hydrogen, except bismuth, and in 
these compounds are trivalent ; while with oxygen, 
most of them exhibit also a higher valence, being 
often pentads. The compounds of the first three 
elements show much analogy, their affinities, as 
usual, decreasing as their atomic weights increase. 
Nitrogen is the most common, as well as important 
element, and may be taken as the type of the group. 



74 LECTURE NOTES. 

Nitrogen. Symbol, N. Atomic weight, 14. 

107. History and Occurrence. Nitrogen was 
discovered in 1772 by Dr. Rutherford. He showed 
that when animals breathe in a closed volum* 
air, it not only becomes laden with impurities from 
the respiration, but that the residual air, freed from 
these impurities, will not support combustion or 
respiration. Its relations to oxygen in the atmos- 
phere were not known for some time. Lavoisier 
gave it the name azote, because of the above men- 
tioned properties. The name nitrogen was after- 
wards given to it by Chaptal. 

It occurs free, but mixed with oxygen, in the 
atmosphere, of which it constitutes about 79 per 
cent, by volume. Combined, it occurs in ammoni- 
um compounds, and in nitrates, of which the most 
important are those of potassium, sodium, and cal- 
cium. It also forms a very essential part of many 
animal and vegetable substances. 

108. Preparation. Nitrogen is most conven- 
iently prepared by removing oxygen from the atmos- 
phere. This may be done in many ways, but is 
usually accomplished by burning phosphorus in a 
bell-jar over water, or by conducting the air over 
red hot copper. These elements combine with the 
. oxygen, leaving nitrogen. 

It may be obtained by heating ammonium nitrite. 
the reaction being as follows : 

NH4NO2 = 2 H 2 + N • 



LECTURE NOTES. 75 

Other ammonium compounds, especially in the 
presence of oxidizing agents, will, when heated, 
give nitrogen. 

109. Properties. Pure nitrogen is a colorless, 
odorless, and tasteless gas, somewhat lighter than 
air, its specific gravity being 0.97. Under very 
strong pressure, and at a very low temperature, it 
condenses to a colorless liquid. It is only very 
slightly soluble in water. It does not burn, nor will 
it support the combustion of anything. It is dis- 
tinguished by its inactive properties, and com- 
bines directly with but very few elements. Indi- 
rectly, it combines with nearly every element, and 
many of these compounds possess remarkably active 
and characteristic properties. Many of its com- 
pounds are unstable at a high temperature, and it 
is a constituent of most high explosives. It is not 
poisonous, although death would ensue in an 
atmosphere of nitrogen, owing to suffocation. Some 
of its compounds, however, are among the most 
active poisons known, all of the exceedingly poison- 
ous alkaloids containing this element. 



The Atmosphere. A mixture of Nitrogen and Oxy- 
gen. Specific gravity, 1. Density, 14.48. 



no. Occurrence and Properties. The atmos- 
phere is the name given to the invisible, gaseous 
envelope surrounding the earth, at the bottom of 



76 LECTURE NOTES. 

which we live. We are aware of its presence by it- 
resistance, motion, pressure, and weight. Its 
resistance is seen when a body passes rapidly 
through it, or, when it is itself in rapid motion, 
that is, when we have what we call a wind. Its 
pressure, being equal in all directions, is not 
noticed until removed in some direction. This 
measured by the barometer, (See Art. 13, I and is 
equal to 1033.3 grams on one square centimeter, or 
about 15 pounds on one square inch, of surface. Its 
weight may be shown by weighing a strong flask 
fitted with a stopcock, exhausting the air, and then 
reweighing, when it is found to have lost weight. 
Careful determinations show that one liter of air, at 
the normal temperature and pressure, weighs 1.29 
grams. 

The height to which the atmosphere extends is 
not accurately known, although observation of the 
time during which the twilight extends to the 
zenith, shows that this is not less than 5.- miles. 
and, possibly, in a very attenuated form, it ma> 
extend to a much greater distance. The reason for 
this uncertainty is that the density decrease- very 
rapidly, but not uniformly, as we ascend. It the 
atmosphere were of the same density throughout, 
its height would be 5.2 miles. 

Since oxygen is necessary to all animal lite the 
atmosphere, which is the source of supply tor this 
important element, is seen to be oi~ the greatest 
importance. The nitrogen being a harm' 



LECTURE NOTES. 77 

inactive substance, serves merely to dilute the oxy- 
gen, which would, otherwise, be too vigorous in its 
action. 

in. Composition of the Atmosphere. The nor- 
mal constituents of the atmosphere are nitrogen, 
oxygen, water! carbon dioxid, ammonia, and traces 
of ozone, nitric acid, hydrogen sulfid, sulfur dioxid, 
and organic matter. These have been very accur- 
ately determined. The relative amounts of nitro- 
gen and oxygen are remarkably constant, in sam- 
ples collected in the most widely separated locali- 
ties ; still, slight variations are observed in different 
localities, which are the effect of purely local causes. 
The percentage composition of the two principal 
constituents, both by weight and by volume, exclu- 
sive of the other ingredients, is found to be as fol- 
lows : 

By Weight. By Volume. 

Nitrogen 77 79 

Oxygen 23 21 

100 100 

The amount of water, or aqueous vapor, varies 
greatly and depends almost entirely upon the tem- 
perature. If a cubic meter of air is completely sat- 
urated with moisture, it is found that at o° it can 
hold 5.4 grams of water, while at 25 the amount is 
22.5 grams, and at 35 , which is about our highest 
summer temperature, the amount is 39.2 grams. 
The quantity actually found in the atmosphere 
is not often more than 60 per cent, of this 



78 LECTURE NOTES. 

amount, and in very dry climates may not exceed 
10 per cent. When the atmosphere is cooled, this 

moisture condenses, and falls as rain, snow or hail. 

The amount of carbon dioxid in the atmosphere 
varies with the locality, the smallest amount being 
found on the sea, and the largest in the neighbor- 
hood of large cities and towns. The average 
amount is about four volumes in 10,000, or about 
0.04 per cent. 

Ammonia is an important constituent of the 
atmosphere, although the amount found is very 
small, averaging about one part in 1,000,000. The 
other constituents are due to local causes and the 
amounts found are exceedingly small. 

112. The Atmosphere a Mixture. The very 
nearly constant composition of the atmosphere led 
chemists for a long time to suppose that it was .1 
definite, chemical compound, of four parts of nitro- 
gen with one of oxygen. Investigation, h<\ 
shows that this cannot be true. All chemical com- 
pounds contain their constituent elements in exact 
proportion to their atomic weights. The proportion 
of nitrogen to oxygen is as 3.85 to 1, Dearly, and 
not as 4 to 1. A mixture of these elements, in the 
right proportion, has all the properties of the atmos- 
phere, and in the mixing there is no variation in 
temperature, as is always the case in chemical com- 
bination. The proportion of nitrogen to oxygen, 
while very nearly constant, is not absolutely s 



LECTURE NOTES. 79 

would be the ease in a chemical compound. When 
air is dissolved in water, the proportion of nitrogen 
to oxygen is quite different from that in the ordi- 
nary atmosphere, and is exactly in accordance with 
the solubility of the two gases in water. This per- 
centage is found to be very nearly, nitrogen, 65, 
oxygen, 35, in the air dissolved in water, which 
variation would not be possible if the atmosphere 
were a chemical compound. 

113. Ventilation. The processes of combustion 
and respiration use up large quantities of the oxy- 
gen in the air, and at the same time produce corre- 
sponding!)' large quantities of carbon dioxid. If 
these take place in a closed room, the air soon 
becomes charged with carbon dioxid, and other 
substances, which are thrown off by the process of 
respiration and from the surface of the body, and 
so becomes too impure to be breathed with safety, 
since air is unsafe to breathe which contains more 
than o. 10 per cent, of carbon dioxid. 

These impure waste products should be removed 
by a proper ventilating shaft, connected with the 
room, a strong draft being maintained by heat, if 
necessary. The stoves, being connected with the 
chimney, as well as the cracks and crevices about 
doors and windows, ventilate a room to some 
extent ; but these are not sufficient, and care should 
be taken to keep our houses, and especially our 
sleeping apartments, properly ventilated, if we would 
preserve our health. 



8<) LECTURE NOTES. 

COMPOUNDS OF NITROGEN WITH HYDROGEN. 

Three compounds of these elements arc known. 
These are : 

Ammonia, NH:j, 
Hydrazin, N2H4, and 
Hydrazoic Acid, HX ; . 

Ammonia. Molecular formula, NH ; . Density, 8.5. 

114. History and Occurrence. Ammonia was 

known to the early alchemists, and is often men- 
tioned in their writings. The name ammonia was 
given to this substance, because it \\ 
obtained from Egypt, being prepared near a temple 
of Jupiter Amnion. 

It occurs in nature in small quantities but quite 
widely diffused, its compounds' being found in the 
air, in soils, and in mineral springs. It is formed 
by the decay of nitrogenous animal matter, and by 
electric discharges in moist air. The latter is 
probably the way in which most of the ammonia in 
nature is formed, and gives the compound, ammo- 
nium nitrate, the action being as follow- : 
N> + O -K-2 H2O = XH;X< I 

115. Preparation. Nitrogen and hydrogen do 

not unite easily to produce ammonia, but can be 
made to do so by passing a silent electric discharge 
through a mixture of these gases. It is most con- 
veniently prepared by heating some ammoniacal salt 



LECTURE NOTES. 8 1 

with calcium oxid, or lime, or with some other 

strong base. The following equation represents the 

action when ammonium chlorid and lime are used : 

2 NH4CI + CaO = CaCl- 2 + H>0 - 2 NH 3 . 

Ammonia is also produced by the dry distillation 
of animal refuse containing nitrogen, such as bones, 
hoofs and horns. The chief commercial source of 
ammonia is a by-product in the manufacture of 
illuminating gas. The coal, which is used for this 
purpose, contains about two per cent, of nitrogen, 
which, in the process of distillation, passes off in 
the form of ammonia ; and this, with other substan- 
ces, is dissolved in the condensed moisture, forming 
the so-called ammoniacal liquor of the gas works. 
From this liquor ammonia is obtained. 

116. Properties. Ammonia is a colorless gas, 
with a characteristic pungent odor, and a sharp, 
caustic taste. It has a very strongly alkaline reac- 
tion upon vegetable colors, neutralizes acids, form- 
ing with them a series of stable compounds called 
the ammoniacal salts. It is one of the lighest gases 
known, its specific gravity being only 0.5S7. Am- 
monia, under ordinary circumstances, is neither 
combustible nor a supporter of combustion, but if it 
be mixed with oxygen it will burn, giving a pale 
yellow flame. 

Ammonia is very soluble in water, the most so of 
any gas known. Under the normal pressure, one 
volume of water at o° will dissolve 1 14s volumes of 
ammonia, and at the ordinary temperature about 



82 LECTURE NOTES. 

750 volumes. If this solution be heated to the boil- 
ing point, all the gas will oe driven off. There is 
probably a weak chemical union between the am- 
monia and the water, forming a compound called 
ammonium hydroxid, ox aqua ammonia, and having 
the molecular formula, NH4OH. Under a pressure 
of seven atmospheres at the ordinary temperature, 
or at a temperature of — 40 at the ordinary pro- 
sure, ammonia becomes a colorless liquid. When 
this liquid is allowed to evaporate, a great amount 
of heat is rendered latent. 

This latter fact, together with the fact that water 
dissolves such a quantity of ammonia, has been util- 
ized in the construction of Carre's machine for mak- 
ing artificial ice. 

117. Hydrazin and Hydrazoic Acid. These are 
both rare substances and have only recently been 
investigated. Hydrazin, N0H4, is a stable gas, 
with a peculiar pungent odor, closely resembling 
ammonia. It is very soluble in water, is a strong 
base, and reduces many metallic salts giving the 
metal. 

Hydrazoic acid, HN3, was discovered by Curtius 
in [890. It is an explosive gas Inning a very dis- 
agreeable, penetrating odor. It is quite soluble in 
water, and quite closely resembles hydrochloric 
acid. It is a strong acid, dissolving most of the 
metals, even when dilute, forming salts, ni 
which are very explosive. It forms an interesting 
salt with ammonia, NH4N3. 



LECTURE NOTES. 83 

118. The Compound Radicals of Nitrogen and 
Hydrogen. When ammonia combines with an acid 
to form a salt, it does so by addition and not by 
substitution, thus : NH 3 + HC1 = NH 4 C1. The 
union of the ammonia with the atom of hydrogen 
in the acid forms a compound radical, NH 4 , which 
is called ammonium. This radical acts very much 
like a monad metal, and may be regarded as such, 
replacing hydrogen in an acid and forming salts, 
called the ammonium, or ammoniacal salts. 

There are two other radicals which are common 

% 

among organic compounds, and which are found 
occasionally in an inorganic compound. These 
are the amido group, NH 5 , and the imido group, 
NH. The former is univalent, the latter bivalent. 

119. The Halogen Compounds of Nitrogen. Ni- 
trogen forms at least one compound with each of 
the halogens. These are among the most violently 
explosive compounds known, and should never be 
prepared except with the greatest care, and in very 
small quantities. 

Nitrogen chlorid, NCI3, is formed when chlorin 
in excess is brought into contact with a warm solu- 
tion of ammonium chlorid, thus : 

NH4CI ■+ 6 CI = NCI3 + 4 HC1. 

It is a thin, yellowish, oily liquid, with a pecu- 
liar, pungent odor. It evaporates quickly in the 
air, and the vapor attacks the eyes. When it is 
heated, or when it is brought into contact with 



84 LECTURE NOTES 

phosphorus, or turpentine, or even exposed to sun- 
light, it explodes with very <4"reat violence. 

Nitrogen bromid, NBr.;. is a red liquid, and hi s 
properties similar to the chlorid. 

Nitrogen iodid, NTs, <>r NHI2. is formed when 
iodine is brought into contact with a concentrated 
solution of ammonia. It is a black powder, which 
explodes with violence when heated, or touched, or 
when thrown into boiling water. 

COMPOUNDS OF NITROGEN WITH OXYGEN. 

There are five compounds of nitrogen with oxy- 
gen. These are : 

Nitrogen monoxid, or nitrous oxid, X_< >. 
Nitrogen dioxid, or nitric oxid. X( ), 
Nitrogen trioxid, N2O3, 

Nitrogen tetroxid, or peroxid, NO2, \j<V. and 
Nitrogen pentoxid, NaOe 

Nitrogen monoxid, or Nitrous oxid. Molecular form- 
ula, N,0. Density, 22. 

120. Preparation and Properties. This com- 
pound is formed when /inc. and certain other 
metals, are dissolved in very dilute nitric acid. It 
is most conveniently prepared l>y heating the com- 
pound ammonium nitrate, \II,\() ; , the action be- 
ing as follows : 

NH 4 NOa 2 HjO • NjO 



LECTURE NOTES. 85 

Nitrous oxid is a colorless gas having a sweetish 
taste and smell. It is somewhat soluble in 'cold 
water, a little more than one volume being: dis- 
solved at o°. It supports combustion almost as 
vigorously as oxygen, with the formation of oxids, 
and liberating nitrogen, it being entirely decom- 
posed at a red heat. 

When nitrous oxid is breathed for a short time, 
it produces a curious kind of nervous excitement or 
intoxication, without entire loss of consciousness, 
and which soon passes away without being followed 
by any evil effects. It is for this reason largely 
employed as an anaesthetic in slight surgical opera- 
tions, especially in dentistry, under the name of 
laughing gas. The anaesthetic effects of this gas 
were observed by Davy, and this substance was the 
first to be employed for such a purpose in a surgi- 
cal operation. In using it, care should be taken to 
have it perfectly pure. When subjected to a pres- 
sure of about 30 atmospheres, it condenses to a col- 
orless liquid. 

Nitrogen dioxid, or Nitric oxid. Molecular form- 
ula, NO. Density, 15. 

121. Preparation and Properties. This oxid is 
formed when nitric acid acts upon copper, or other 
metals of a like nature, or upon easily oxidizable 
substances. In this action hydrogen is liberated, 
which, in the nascent state, decomposes more of the 
nitric acid, forming the oxid, thus : 



86 LECTURE NOTES. 

3 Cu + 8 HNOs = 3 Cu(N0 8 ) 2 + 4 HjO + 2 X< > 
Nitric oxid is a colorless gas, which is only very 
slightly soluble in water. It dissolves easily in an 
aqueous solution of ferrous salts, imparting a dark 
brown color to the solution. This color is due to 
the formation of a peculiar compound, which, if 
ferrous sulfate is used, has the formula, FeSC^NO. 
If this compound be heated, the nitric oxid is en- 
tirely expelled. Nitric oxid is not combustible, 
but supports the combustion of certain substances, 
since, if previously ignited, they will continue to 
burn in this gas. Its most characteristic property 
is its direct union with oxygen, forming nitrogen 
trioxid, or nitrogen peroxid. Both of these sub- 
stances have a dark reddish brown color, and so if 
nitric oxid is exposed to the air, it at once becomes 
reddish brown, owing to the formation of one of 
these compounds. It also unites directly with 
chlorin, forming nitrosylchlorid, NOC1. 

Nitrogen trioxid. Molecular formula, N-..0 .. Den- 
sity, 38. 

122. Preparation and Properties. When easily 
oxidizable substances, such as starch, sugar, or 
arsenious oxid, are heated with nitric acid, nitro- 
gen trioxid is formed, thus: 

AssOs + 2 HNO3 = As,0 5 + H a O + NA. 

It is also formed when four volumes oi~ nitric 
oxid, and one of oxygen, are mixed together. If 



LECTURE NOTES. #87 

these vapors be led through a freezing mixture, a 
dark blue liquid is formed, which is nearly pure 
N2O3. This substance begins to decompose at o°, 
forming nitric oxid, and nitrogen peroxid. With 
water, this compound forms nitrous acid, which is 
very unstable, and only exists at low temperatures. 

Nitrogen tetroxid, or peroxid. Molecular formula, 
N 2 4 , or N0 2 . Density, above 140 , 23. 

123. Preparation and Properties. This com- 
pound may be formed by mixing together two vol- 
umes of nitric oxid, and one volume of oxygen ; or, 
by heating dry lead nitrate, the following equation 
representing the action : 

Pb(N03>2 = PbO + + 2 NO2. 

Nitrogen peroxid furnishes an interesting exam- 
ple of dissociation at ordinary temperatures. If the 
substance be passed through a freezing mixture, it 
condenses to a colorless liquid, which becomes a 
white solid at — 9 . At this temperature its 
molecular formula is N2O4. At about o° it begins 
to decompose, and the liquid becomes yellow. At 
22 it boils, and becomes a dark reddish brown 
gas, which grows darker as the temperature is in- 
creased, until it is almost black. At 140 the dis- 
sociation is complete, the density being 23, which 
corresponds to the molecular formula NO2. Nitro- 
gen peroxid is soluble in water, forming nitric acid 
and nitric oxid. 



88 LECTIKK. NOTES. 

Nitrogen pentoxid. Molecular formula, N.O.-,. Mol- 
ecular weight, 108. 

124. Preparation and Properties. Nitrogen 
pentoxid may be prepared by the action of phos- 
phorus pentoxid on nitric acid, thus : 

P2O5 + 2 HNOs = 2 HP0 3 f- N 
It is a colorless, crystalline solid, which melts at 
30 , and boils at 47 , being entirely decomposed 
into nitrogen peroxid and oxygen. It combines 
with water with great energy, giving off much heat, 
and forming nitric acid. 

125. The Oxy-acids of Nitrogen. Nitrogen 
forms three oxy-acids. These are : 

Hyponitrous acid, HNO, 

Nitrous acid, HN(X>, and 

Nitric acid, HNOs. 
Only the nitric acid is important. The other two 
are unstable and only exist at low temperatures. 
They form salts which are called hvponitrites and 
nitrites, respectively, some of which are used quite 
extensively. 

Nitric Acid. Molecular formula, HNO ; . Molecular 
weight, 63. 

126. History and Occurrence. Nitric acid has 
been known since the 8th century, having first 
been made by the Arabian alchemist Geber, It- 
true composition was determined by Cavendish in 



LECTURE NOTES. 89 

1785. It was known to the alchemists under the 
name of aqua fortis : 

It is produced in small quantities by electric dis- 
charges in the atmosphere. Its salts, the nitrates, 
are found in quite large quantities, the principal 
ones being potassium nitrate, KNO3, called also 
saltpeter, or niter, and sodium nitrate, NaNOs, 
called Chili saltpeter. The former is found in large 
deposits in India, and the latter in parts of Chili 
and Peru, where it was formed by the oxidation of 
nitrogenous organic matter, in the presence of 
potassium and sodium bases. 

127. Preparation. Nitric acid is always pre- 
pared by the action of sulfuric acid on a nitrate, 
usually of sodium or potassium. About equal 
weights of the nitrate and sulfuric acid are mixed 
in a retort and gently heated, the action being rep- 
resented by the following equation: 

KNO3 + H 2 S04 = KHSO4 + HXO3. 
If the heat is sufficiently increased, the acid 
potassium sulfate formed, acts upon more of the 
nitrate, forming more nitric acid, thus: 

KHSO4 + KNO3 = K2SO4 + HNO3. 

128. Properties. Nitric acid, when pure, is a 
colorless fuming liquid, but it usually has a faint 
yellow color, owing to the presence of some of the 
oxids of nitrogen, which, being produced by its par- 
tial decomposition, dissolve in the acid producing the 
color. It is a strong acid, acting on most of the met- 



90 LECTURE NOTES. 

als with great vigor. Nitrogenous organic substan- 
ces, such as silk, and wool, are colored yellow by this 
acid, while many other organic compounds, such 
as cotton and glycerol are converted into violently 
explosive substances. Its specific gravity is 1.53 
when concentrated. If the acid is heated, it begins 
to boil at 86°, being partially decomposed into 
water, nitrogen peroxid, and oxygen. By further 
heating, the boiling point continues to rise slowly 
until it reaches the temperature 12 1°, when it dis- 
tils without further change of temperature, or com- 
position, the strength of acid being 68 per cent., 
and the specific gravity 1.42. 

Nitric acid is a very powerful oxidizing agent, 
owing to the ease with which it parts with oxygen. 
Sulfur and phosphorus are oxidized to sulfuric and 
phosphoric acids, and compounds which exist in a 
low state of valence, are oxidized to a higher state 
by this acid. Its salts, the nitrates, are decomposed 
by heat, giving oxygen, and so are sometimes used 
as oxidizing agents. 

129. Aqua Regia. Certain of the metals, par- 
ticularly gold and platinum, are not dissolved by 
any single acid. In order to effect a solution of 
these metals, a mixture of three parts of hydro- 
chloric, and one of nitric acid, is employed. These 
two acids act upon, and decompose each other, with 
the liberation of chlorin and a volatile compound 
called nitrosylchlorid, the action being as follows : 
3 HC1 + HNO3 = 2 H,Q + N( >C1 CI,. 



LECTURE NOTES. 91 

This mixture of acids is called aqua regia, and 
the solvent action on the gold or platinum is due to 
the fact that free chlorin is formed, which com- 
bines with the metal forming a soluble chlorid. It 
therefore follows, that when a metal is dissolved 
in aqua regia, a chlorid is always formed. 

Phosphorus. Symbol, P. Atomic weight, 31. 

130. History and Occurrence. Several chemists 
claim the honor of having discovered this element. 
The best evidence, however, seems to prove that it 
was first prepared by Brand, in 1669, who obtained 
it from urine. 

Phosphorus never occurs free in nature, although 
in combination with other elements it is very widely 
distributed, being found, in quantities more or less 
minute, in almost every substance on the earth's 
crust. Its most important compound is calcium 
phosphate, Ca3(P04>2, which is found in immense 
quantities in the so-called phosphate beds of South 
Carolina, and in the guano beds of the Caribbean 
islands. It is taken up by the plants from the 
soil, and forms an essential constituent of the fruit 
and seeds. From the plants phosphorus finds its 
way into the animal body where it is found in 
the brain and tissues, and especially in the bones, 
about 50 per cent, of which consists of calcium 
phosphate. When the tissues waste away, they are 
replaced by fresh material, the phosphorus being 



92 LECTURE NOTES. 

excreted in the urine, chiefly in the form of 
sodium ammonium phosphate, or microcosmic salt, 
Na(NH 4 )HP0 4 , 4 H 2 0. 

131. Preparation. Phosphorus is almost always 
prepared from bones, which are treated in various 
ways for the extraction of the organic materials. 
The remaining portion is then burned, forming 
what is called bone-ash, which is almost entirely 
composed of calcium phosphate. The extraction of 
the phosphorus from this compound is a three-fold 
process, and quite complicated. The bone-a>h is 
first acted upon by sulfuric acid, which converts the 
insoluble calcium phosphate into soluble acid cal- 
cium phosphate and insoluble calcium sulfate, thus : 
Ca 3 (P0 4 )2 + 2 H2SO4 = 2 CaS0 4 + CaH 4 (PCV),>. 

The solution is poured off, evaporated to dryness, 
and then heated to redness, forming calcium meta- 
phosphate, thus : 

CaH 4 (P0 4 ) 2 = 2 H2O + Ca(P< 

The calcium metaphosphate is then mixed with 
charcoal and strongly heated in earthen retorts, 
when the phosphorous distils off and is collected 
under water, the following equation representing 
the action : 

3 Ca(P0 3 >2 -f 10 C = Ca 3 (P0 4 >2 + 10 CO + P 4 . 

In this way only two-thirds of the phosphorus is 
driven off. To obtain the whole of it, sand may la- 
added to the mixture with the carbon, when calci- 



LECTURE NOTES. 93 

urn silicate is formed, all of the phosphorus being 
driven off, thus : 

2 Ca(P0 3 ) 2 + io C + 2 Si0 2 = 

2 CaSiO.s + io CO +P 4 . 

The crude phosphorus thus obtained is purified 
by re-distillation and pressing through wash-leather, 
or by oxidizing the impurities, and is then cast in 
copper 'tubes, all the operations being carried on 
under water. 

132. Properties. Ordinary phosphorus is a 
slightly yellow, or almost colorless, transparent, 
crystalline solid, which is brittle at a low tempera- 
ture, but at 1 5 becomes soft and wax-like, being 
easily cut with a knife. It has a specific gravity of 
1.83, melts at 44 , and boils at 290 , yielding a 
colorless vapor. This vapor of phosphorus has a 
density of 62, which shows that its molecule con- 
sists of four atoms. Phosphorus is insoluble in 
water, but dissolves readily in sulfur monochlorid, 
and especially in carbon disulfid, from which solu- 
tion it separates in fine crystals. 

Phosphorus is an exceedingly inflammable 
substance, which takes fire at a little above 
its melting point, burns with a bright flame, 
forming phosphorus pentoxid, P2O5. For this 
reason it is always kept under water. When 
in contact with moist air, it oxidizes slowly, 
and on this account appears luminous in the dark. 
This phenomenon is known ^phosphorescence, and 
is one of its most characteristic properties. It gives 



94 LECTURE NOTES. 

off white fumes which have a garlic-like odor, and 
forms ozone. [See Art. 45.] It is a violent 
poison, acting on the blood and depriving it of oxy- 
gen. 

133. The Allotropic Forms of Phosphorus. There 
are two, possibly three, allotropic forms of phos- 
phorus, which differ from each other in a very 
marked degree. If the common, or yellow phos- 
phorus, be heated in a gas which has no action 
upon it, or in a closed vessel, to 300 , it is changed 
into a reddish-brown, amorphous solid, which is 
known as red, or amorphous phosphorus. This sub- 
stance has a specific gravity of 2.14, does not oxi- 
dize in the air, nor will it take fire until heated to 
260 . It is not poisonous, and is insoluble in car- 
bon disulfid. When heated to 360 , it changes 
back into the common variety. 

A third modification is formed when the amor- 
phous phosphorus is heated under pressure to 
or, when heated for a long time at a high tempera- 
ture in contact with metallic lead. It is a dark 
crystalline mass known as metallic phosphorus, has 
a specific gravity of 2.34, and conducts electricity. 

134. Uses. Phosphorus is used quite exten- 
sively in the laboratory in making certain organic 
compounds which are employed in the manufacture 
of aniline dyes. It is very extensively employed 
in the manufacture of matches, being used in con- 
nection with other substances, in making th< 



LECTURE NOTES. 95 

with which the common or lucifer matches are 
tipped, and the surface upon which the so-called 
safety matches are lighted. The red phosphorus is 
nearly always used for this purpose. 

COMPOUNDS OF PHOSPHORUS WITH HYDROGEN. 

There are three compounds of phosphorus and 
hydrogen known. The}' are distinguished by the 
state of aggregation in which they exist, as 

Gaseous hydrogen phosphid, or Phosphin, PH3, 

Liquid hydrogen phosphid, P2H4, and 

Solid hydrogen phosphid, P4H9. 

Phosphin. Symbol, PH 3 . Density, 17. 

135. Preparation and Properties. This sub- 
stance is best prepared by heating phosphorus in a 
solution of sodium or potassium hydroxid, when 
phosphin and a hypophosphite are formed, thus : 

3 XaOH + Pi + 3 H2O == 3 NaHoPOo + PH 3 . 

It is also formed when a metallic phosphid is 
thrown into water. 

Phosphin is a colorless gas, having a very disa- 
greeable odor somewhat like rotten fish. The pure 
gas takes fire at about ioo°; but the gas as prepared 
above contains traces of the liquid hydrogen phos- 
phid, which render it spontaneously inflammable, 
so that if it be allowed to pass through water, each 
bubble as it reaches the surface ignites with a slight 



96 LECTURE NOTES. 

explosion, forming a beautiful ring of phosphorus 
pentoxid, which shows a remarkable vortex motion. 
Phosphin is a very poisonous gas, which acts upon 
the blood, causing difficulty in breathing, and death. 
It is a weak base, and forms compounds resembling 
those formed by ammonia, which are called phos- 
phonium compounds. The liquid and solid hydro- 
gen phosphids are not of especial importance. 

136. The Halogen Compounds of Phosphorus. 
Phosphorus forms compounds with each of the hal- 
ogen elements, in the most cases by direct union. 
The chlorids are the most important compounds. 

If dry chlorin be led over phosphorus, care being 
taken to have an excess of phosphorus, there is 
formed phosphorus trichlorid, PCI;;. If the chlorin 
be in excess the pentachlorid, PCI5, is formed. 

The trichlorid is a colorless liquid, which fumes 
strongly in the air, and boils at 76 . When 
brought into contact with water, it decomposes into 
hydrochloric and phosphorous acids, thus : 
PCI3 + 3 H,0 = 3 HC1 -f- H3PO3 

The pentachlorid is a yellowish white crystalline 
solid, which is much used in organic chemistry tor 
replacing the hydroxyl group with chlorin. 

Phosphorus forms two bromids, two iodids, and 
one fluorid. Their properties are quite similar to 
the corresponding chlorids. 

137. Compounds of Phosphorus with Oxygen. 
There are two compounds of phosphorus witli oxy- 



LECTURE NOTES. 97 

gen, phosphorus trioxid, P2O3 or P4O6, and phos- 
phorus pentoxid, P2O5 The trioxid is formed 
when phosphorus is allowed to oxidize in a limited 
supply of air. It is a white amorphous solid, with 
an odor like garlic, and, when dry, does not redden 
litmus. It dissolves in water forming phosphorous 
acid. 

Phosphorus pentoxid is always formed when 
phosphorus burns in the air, or in oxygen. It is a 
white, amorphous powder, is very deliquescent, and 
forms with water phosphoric acid. It is used in the 
laboratory for drying gases, and for removing the 
elements of water from certain compounds. [See 
Art. 124.] 

compounds of phosphorus with oxygen and 
hydrogen. 

138. The Oxy-acids of Phosphorus. There are 
at least five oxy-acids of phosphorus, although two 
of them are derivatives of one of the others. They 
are : 

Hypophosphorous acid, H3PO2, 
Phosphorous acid, H3PO.3, 
Phosphoric acid, H3PO4, 
Pyrophosphoric acid, H4P2O7, and 
Metaphosphoric acid, HPO3. 
The last two are derivations of the third acid. 

139. Hypophosphorous Acid, H3PO2. The salts 
of this acid, the hypophosphites, are formed when- 



98 LECTURE NOTES. 

ever phosphorus is heated with a soluble base. 
If barium hydroxid, Ba(OH)j, is used, barium 
hypophosphite, Ba(HaP02)2, is formed; and by the 
addition of sulfuric acid to this compound hypo- 
phosphorous acid is obtained. It is a white crys- 
talline solid, which upon strongly heating, decom- 
poses into phosphoric acid and phosphin. Although 
this acid contains three atoms of hydrogen in each 
molecule, only one of them is replaceable, and so 
it is a monobasic acid. [See Art. 31.] 

140. Phosphorous Acid, H 3 P0 3 . This acid is best 
prepared by the decomposition of phosphorus tri- 
chlorid by means of water, thus : 

PCI3 + 3 H,0 = 3 HC1 + H 3 P0 3 . 
It is a white crystalline solid, having a strong 
garlic-like odor, and taste, and on strongly heating, 
decomposes into phosphoric acid and phosphin. 
Only two of the hydrogen atoms are replaceable, 
and it is therefore a dibasic acid. Its salts are 
called phosphites. 

141. Phosphoric Acid, H :i P0 4 . This acid, which 
may be prepared in many ways, is best prepared by 
the oxidation of phosphorus by means of nitric 
acid. Red phosphorus is commonly employed in 
this reaction, which is as follows : 

P 3 + 5 HN0 3 + 2 H,0 = 3 HsPQ* -h 5 N< >. 

It may also be prepared by dissolving phospho- 
rus pentoxid in hot water. Commercially it is 
prepared from bone-ash. 



LECTURE NOTES. 99 

Phosphoric acid is a white crystalline solid, hav- 
ing no odor, but an agreeable acid taste. It is 
very soluble in water and forms salts which are 
called phosphates. It is a tribasic acid and so there 
are three classes of phosphates, two acid and one 
normal. These are also called primary, secondary 
and tertiary phosphates, according as one, two, or 
three atoms of hydrogen are replaced by a base. 

If phosphoric acid is heated to 215 , it loses water 
and forms pyrophosphoric acid, thus : 

2 H3PO4 = H4P2O7 + H2O. 
Its salts, the pyrophosphates are often formed by 
heating secondary phosphates. It is a tetrabasic 
acid. 

If either phosphoric, or pyrophosphoric acid is 
heated to 400 , more water is given off, and there 
is formed metaphosphoric acid, thus : 
H3PO4 = HPO3 + H 2 0. 

It is a glassy transparent solid and often called 
glacial phosphoric acid. It melts at a red heat, 
but does not decompose. It is a monobasic acid, 
and its salts may be formed by heating the primary 
phosphates. 

142. Compounds of Phosphorus with Sulfur. 
These two elements combine to form several com- 
pounds, which are divided into two classes, called 
sulfur phosphids, and phosphorus sulfids. They 
are formed by direct union of the elements, and, in 
many cases, with explosive violence. Phosphorus 



IOO LECTURE NOTES. 

pentasulfid, P 2 S. 5 , is the only one of importance, and 
is used in making organic preparations, for the pur- 
pose of replacing oxygen with sulfur. It is a gray- 
ish colored solid, which boils at 51 8°, and its vapor 
is sometimes used to obtain a constant high tem- 
perature. 

Arsenic. Symbol, As. Atomic Weight, 75. 

143. History and Occurrence. Certain com- 
pounds of arsenic were known to the ancients, and 
the trioxid was known to Geber, in the eighth cen- 
tury. These compounds of arsenic were highly 
valued by the alchemists, and employed by them 
in their attempts to transmute the base metals into 
gold. The elefnent itself was first obtained about 
the end of the seventeenth century. 

Arsenic occurs free in nature, in small quantities, 
and in a few localities. Combined with other ele- 
ments, it is quite widely distributed. It occurs in 
combination with sulfur, and oxygen, and in com- 
pounds with the metals, called arsenids. Small 
quantities of arsenic occur in connection with cer- 
tain metallic sulfids, and this is one of its important 
sources. 

144. Preparation. If ores/containing arsenic, 
are roasted in a furnace, so constructed as to admit 
a plentiful supply of air, the trioxid is formed; 
This substance, which is quite volatile, is collected 
in suitable chambers. The arsenic trioxid is then 



LECTURE NOTES. IOI 

mixed with charcoal, and heated in earthenware 
tubes, when the free arsenic volatilizes, and collects 
in the cooler portion of the tubes. The action is as 
follows : 

As 2 3 + 3 C = 3 CO + As 2 . 

145. Properties. Arsenic is a steel-gray, crys- 
talline solid, having a specific gravity of 5.72. 
When heated under ordinary pressure it does not 
melt, but passes at once from the solid to the gase- 
ous state. It will fuse under strong pressure. The 
vapor of arsenic has a lemon-yellow color, and a 
strong garlic-like odor, probably due to a partial 
oxidation of the element. When heated in the air 
it takes fire, and burns with a bright white flame. 
The vapor of arsenic has a density of 150, which 
shows that the molecule contains four atoms. Ar- 
senic and most of its compounds are very poisonous. 

If arsenic is made to sublime in a stream of hy- 
drogen gas, it will deposit in a black, or gray amor- 
phous powder, which is an allotropic form. This 
has a specific gravity of 4.71, but does not differ 
materially in chemical properties from the first form. 
When heated to 360 , it changes back to the crys- 
talline variety. 

The relations of arsenic to the other elements is 
peculiar. In the free state it is quite metallic in its 
physical properties. In its compounds with the 
non-metallic elements it very closely resembles 
phosphorus, while with the metals it is analogous 



102 LECTURE NOTES. 

to sulfur, since the two elements can mutually re- 
place each other. 

COMPOUND OF ARSENIC WITH HYDROGEN. 

Hydrogen Arsenid, or Arsin. Molecular formula, 
AsH 3 . Density, 39. 

146. Preparation and Properties. In order to 
prepare this substance pure, an alloy of zinc and 
arsenic, known as zinc arsenid, is decomposed by 
dilute sulfuric acid, thus : 

Zn 8 As 2 + 3 H2SO4 = 3 Z11SO4 + 2 AsH 3 . 

It is also formed when nascent hydrogen acts 
upon an arsenic compound. 

Arsin is a colorless gas, with a garlic-like odor. 
It burns in the air with a bluish-white flame form- 
ing arsenic trioxid, AS2C3. If the gas be p 
through a heated glass tube, it is decomposed, and 
arsenic condenses on the tube, in the form of a shin- 
ing black deposit, which is known as the arsenic 
mirror. Arsin is an exceedingly poisonous sub- 
stance, a single bubble of the pure gas being suffi- 
cient to cause death. Great care should therefore 
be observed in experimenting with this gas. 

147. Marsh's test for Arsenic. Since arsenic 
and its compounds are so poisonous, and since they 
are used quite extensively in the arts and manufac- 
tures, cases of poisoning by arsenic, accidental or 
otherwise, are not uncommon. It is important foi 



LECTURE NOTES. I03 

the chemist, therefore, to be familiar with methods 
for its detection. One of the best methods depends 
upon the properties of arsin above described, and is 
known as Marsh's test. 

The suspected substance is treated in such a way 
as to separate the arsenic from all organic matter. 
The arsenic, usually in solution, is then placed in 
an apparatus containing pure zinc and sulfuric acid. 
The nascent hydrogen thus generated, combines 
with the arsenic forming arsin, which is then made 
to pass through a hard glass tube, heated in one or 
more places. If arsenic is present, the arsin is de- 
composed, and an arsenic mirror is formed in the 
tube. As the decomposition is not complete in the 
tube, if the gas issuing from the end is ignited, and 
a piece of cold porcelain be held in the flame, there 
will be formed a black spot, the arsenic mirror, on 
the porcelain. By exercising care in the operation, 
the minutest traces of arsenic can, by this method, 
be detected. 

148. The Halogen compounds of Arsenic. Ar- 
senic forms one compound with each of the halogen 
elements, acting as a triad in each case. The ele- 
ments combine directly, and exhibit a strong affinity 
for each other. 

Arsenic trichlorid, AsCls, is best prepared by act- 
iug upon arsenic trioxid with hydrochloric acid, 
thus: 

AS2O3 4 6 HC1 = 3 HoO + 2 AsCls. 



104 LECTURE NOTES. 

Arsenic trichlorid is a colorless, oily, very poi- 
sonous liquid, which boils at 134 . It is soluble in 
a small amount of water, but if the amount of water 
present is excessive, it decomposes into the trioxid 
and hydrochloric acid. The other halogen com- 
pounds are quite similar in their chemical proper- 
ties. 

COMPOUNDS OF ARSENIC WITH OXYGEN. 

There are two compounds of these elements, 
Arsenic trioxid, AS2O3, and 
Arsenic pentoxid, AS2O5. 

Each forms an acid when dissolved in water. 

Arsenic trioxid. Symbol, As>0 3 , or As 4 O t; . Vapor 
density, 198. 

14Q. Preparation and Properties. This sub- 
stance, which is known commercially as white ar- 
senic, is found in nature as the mineral arsenoiiie. 
It is prepared by roasting arsenical ores with free 
access of air. The oxid is volatilized and the va- 
pors are collected in what are called poison chambers t 
and purified by re-sublimation. 

Arsenic trioxid is a white crystalline solid, which 
is odorless, but has a metallic, sweetish taste. It 
has a specific gravity of 3.73, and volatilizes with- 
out fusion at 21 8°, giving a vapor, whose density 
corresponds to the formula, As 4 0«. Under slight 



LECTURE NOTES. I05 

pressure it can be fused, and if it be then heated for 
some time, and at a high temperature, it forms, on 
cooling, an allotropic modification, which is a white 
mass, at first transparent, but soon becomes opaque 
and like porcelain. It is slightly soluble in water 
forming a weak acid. 

150. Arsenic Pentoxid, As 2 5 . This substance is 
formed by treating arsenic trioxid with an oxidiz- 
ing agent, in the presence of water. This forms 
arsenic acid, which b}^ heating gives off water, 
leaving the pentoxid. 

It is a white porous solid, which dissolves in wa- 
ter quite easily, forming arsenic acid. When very 
strongly heated, it decomposes into the trioxid and 
oxygen. 

151. The Oxy-acids of Arsenic. The oxy-acids 
of arsenic correspond exactly to those of phospho- 
rus, with this exception, there is no hypo-arsenious 
acid. 

Arsenious acid, H3ASO3, is formed by dissolving 
arsenic trioxid in water. It is a weak, tribasic acid, 
whose salts are quite important. The copper salt, 
CuHAsOa, is the well-known compound called Paris 
green. 

Arsenic acid, H3ASO4. is best formed by acting 
upon the trioxid with nitric acid, thus : 
AS2O3 + 2 HNO3 + 2 H,0 = 2 H3ASO4 -f N2O3. 

It is used in calico printing and in the manufac- 



iob LECTURE NOTES. 

ture of certain anilin dyes. Its salts, the arsenates, 
correspond very closely to the phosphate. 

Pyro-and met-arsenic acids are formed by heat- 
ing arsenic acid, the former being formed at 
and the latter at 200 . 

COMPOUNDS OF ARSENIC WITH SULFUR. 

There are three compounds of these elements 
known. They are, 

Arsenic distil fid, As-.-Sj, 
Arsenic trisulfid, AS2S8, and 
Arsenic pentastilfid, As 

152. Arsenic Disulfid, As_>S_> This compound is 
found in nature as the mineral Realgar^ forming 
ruby-red crystals. It may be formed artificially by 
fusing together arsenic and sulfur in the right pro- 
portions. This product is known as ruby sulfur. 
and is employed in the arts for the manufacture of 
the so-called Indian-, or white-fire, and als 
pigment. It was one of the compounds of arsenic 
known to the ancients. 

153. Arsenic Trisulfid, As-.-S;. This compound 
is found in nature as the mineral Orpitnent, form 
ing bright yellow crystals. It is formed when hy- 
drogen sulfid, is passed through an acid solution of 
arsenic trioxid, thus: 

As.O; I 3 II.S 3 H a • AsaS 
This compound was formerly much used 



LECTURE NOTES. 1 07 

pigment, and was also known to the ancients. 

An impure compound, consisting of a mixture of 
arsenic trioxid and trisulfid, and known commer- 
cially as King' s yellow is formed, when arsenic tri- 
oxid and sulfur are heated together. 

154. Arsenic Pentasulfid, As. 2 S 5 . If hydrogen 
sulfid is led through a solution of arsenic acid, 
there is formed a mixture of arsenic trisulfid and 
sulfur The pentasulfid can be formed by fusing 
together arsenic trisulfid and sulfur, or better, by 
decomposing some sulfarsenate with dilute hydro- 
chloric acid, thus : 

2 K3ASS4 + 6 HC1 = 6 KC1 +3 H- 2 S + AS2S5. 
It is a bright yellow powder which can be sub- 
limed without decomposition. 

155. The Sulfo-Salts. If certain sulfids, such 
as those of arsenic, antimony, tin, gold, and plati- 
num, are treated with a solution of some alkaline 
sulfid, such as potassium sulfid, K- 2 S, or ammonium 
sulfid, (NH^aS, they dissolve, with the formation of 
a peculiar class of compounds, which have the 
same relation to the sulfids, as do the common salts 
to the oxids. These compounds are true salts, but 
have the oxygen replaced by sulfur, and in order to 
distinguish them, they are called sulfo salts. Thus, 
if arsenic trisulfid be dissolved in a solution of po- 
tassium sulfid, potassium sulfarsenite is formed, 
thus : 

As 2 Sa + 3 K- 2 S = 2 K 8 AsS: ; . 



Io8 LECTURE NOTES. 

In the same way the pentasulfid forms potassium 

sulfarsenate, K3ASS4. 

These compounds are mostly soluble in water, 
and decomposed by dilute acids. They are formed 
in the separation of the above mentioned metals 
from others of the same group. 

Antimony, (Stibium). Symbol, Sb. Atomic 
Weight, 120. 

156. Occurrence and Preparation. Antimony 

occurs occasionally free in nature, but more com- 
monly in combination with sulfur, as SHbniU, 
Sb.jS 3 , and with sulfur and the metals in many ores. 
It is prepared by roasting the ores with free ac 
of air, when the trioxid, SD0O3, is formed. 

The trioxid is then mixed with carbon and strong- 
ly ignited, which gives the metal, the whole op< 
tion being analogous to the one for obtaining ar- 
senic. (See Art. 144). It can also be obtained 
from Stibnite, by fusing it with iron, thus: 
SbaSs + 3 Fe = 3 FeS + 2 Sb. 

157. Properties and Uses. Antim >u> is a bril- 
liant, bluish-white metal, having a leaf) 

line structure, and so hard, and brittle, that it may 
be powdered in a mortar. It has a specific gra 
of 6. 71, melts at 450°, and volatilizes at a bri 
red heat. It does not oxidize in the air at th< 
dinary temperature, but, when healed to redness, 



LECTURE NOTES. 109 

burns, forming the oxid, SboOs. It dissolves in 
concentrated hydrochloric acid, in concentrated sul- 
furic acid, and in aqua regia, but with nitric acid 
it is oxidized to the pentoxid, Sb90o. 

Its principle use is in the manufacture of alloys, 
of which the most important is type-metal, which 
is composed of lead, tin and antimony. It is also 
employed for the preparation of tartar emetic, and 
other pharmaceutical products. * 

In its physical properties, antimony closely re- 
sembles the metals, but chemically, it is much like 
arsenic. Only a few of its compounds will be con- 
sidered at this time. 

158. Stibin, SbH 3 . This substance is in every 
way analogous to arsin, and may be prepared in a 
similar way. It is a colorless gas, having a disa- 
greeable odor and taste. It is poisonous but not 
nearly so much so as arsin. It burns with a pale 
flame, and, if passed through a hot tube, decom- 
poses, forming a mirror like that of arsenic, from 
which it may be distinguished in man}- wa}'S. 

159. The Halogen compounds of Antimony. An- 
timony forms compounds with each of the halogens, 
uniting with them directly. They are quite like 
the corresponding compounds of arsenic. The only 
one of much importance is the trichlorid, SbCl3- 
This may be formed by dissolving the metal, the 
trioxid, or the trisulfid, in hydrochloric acid. It is 
a soft, deliquescent substance, which has been 



HO LECTURE NOTES. 

known since the time of the early alchemists, hav- 
ing been called by them hitter of antimony. It 
melts at 7 2° and boils at 235 . It is soluble in a 
small quantity of water, but with a larger quantity 
of water forms an insoluble white powder, which is 
antimony oxy-chlorid, SbOCl, and which was 
known to the alchemists as powder of Algaroih. 

160. The Oxids and Oxy-acids of Antimony. 
There are three oxids of antimony known. They 
are, 

Antimony trioxid, SD2O3, 
Antimony tetroxid, SD2O4, and 
Antimony pentoxid, SbsOg. 
The trioxid acts as a base in the presen 
acids, and as a weak acid in the presence of strong 
bases, while the othc. two have weak acid pi 
ties. The tetroxid is regarded by many as a union 
of the trioxid and pentoxid, and is formed when 
either of the others is heated, Strongly in the air. 

The acids are not very well defined, but corre- 
spond to those of arsenic. They torn; 
stable salts with the stronger bases Most of the 
soluble salts of antimony when in contact wit: 
quantities of water, form insoluble basic compounds. 
161. The Sulfids of Antimony. There are two 
of these compounds, a trisulfid, SbjS.,, and a penta- 
sulfid, Sb-jS.-,. The trisulfid, which is the only one 
of importance, is found in nature as the mi 
Stib)iitc\ in steel-gray lustrous crystals [f hy 



LECTURE NOTES. Ill 

sulfid is passed through an acid solution of antimo- 
ny trichlorid, an orange-red precipitate is thrown 
down. This is the trisulfid, but contains water, 
and if it be heated in a stream of carbon dioxid, it 
leaves a gray solid, which is the pure trisulfid. 

Bismuth. Symbol, Bi. Atomic Weight, 208. 

162. Properties. This element is connected 
with this group by its valence, and the analogy of 
some of its compounds. Its physical properties 
and high atomic weight class it with the metals. 
In its chemical properties it very closely resembles 
antimony and the metals. It forms no compound 
with hydrogen. Its oxid forms no acid, but is 
strongly basic. It will therefore be considered 
among the metals. 

Boron. Symbol, B. Atomic Weight, 11 

163. Occurrence, Preparation and Properties. 

This element is generally classed with the non- 
metals, although it seems to be isolated among 
them. On account of its trivalent nature it is some- 
times placed in the nitrogen group, and so is con- 
sidered here. In its free state it resembles carbon 
and silicon, but in most respects it is more like the 
metal aluminum. 

It is found in nature as boric acid, and in the 
form of borates, chiefly of sodium and magnesium, 



[12 LECTURE NOTES. 

the principal localities being in Tuscany and Cali- 
fornia. 

It may be prepared by igniting boron trioxid with 
sodium, with exclusion of air. On treating the 
fused mass with water, the boron is left as a dark 
brown amorphous powder. If the amorphous boron 
be fused in a crucible with aluminum, the whole 
being placed in a larger crucible with powdered 
charcoal, the boron crystallizes, and may be sepa- 
rated from the aluminum by dissolving the latter in 
hydrochloric acid. The crystals thus obtained are 
not perfectly pure boron, but contain both alumi- 
num and carbon. They are more or less colored, 
are very brilliant, and almost as hard as diamond. 
and are called adamantine boron 

It was long supposed that boron formed no com- 
pound with hydrogen, but it has been recently dis- 
covered that such a compound exists. It somewhat 
resembles slibin, and is very unstable I the tri 
oxid mixed with carbon be heated in nitrogen, there 
is formed boron nitrid, BN, a white amorphous 
powder. 

164. Boric Acid and its Salts. Boric acid is 
found free in nature, in the region of extinct volca- 
noes, the most important localities being in Tusca- 
ny, and in California. It may be prepared by de- 
composing a solution oi borax, with sulfuric acid, 
thus : 
Na a B 4 07 + H2SO4 + 5 ^1^ NaaSO* + 4 Htl 



LECTURE NOTES. 113 

It is a white solid, crystallizing in glistening 
scales, which are somewhat soluble in cold water. 
It is easily soluble in hot water, and in alcohol, and 
if the latter solution be ignited, it burns with a 
characteristic green flame. 

When boric acid is heated to ioo°, it loses water 
and forms metaboric acid, HBOo. At 140 it loses 
more water and forms tetraboric, or pyroboric acid, 
H-iBiOi. When any of these acids are strongly ig- 
nited, all the water is driven off, and there remains 
boron trioxid, B2O3. 

There are no salts of normal boric acid known. 
The metaborates are unstable, while the tetrabo- 
rates are very stable. Sodium tetraborate, or Borax, 
Na-2B 4 07, is the most important compound of boron. 
It finds abundant use in the arts as a flux, and dis- 
solves most of the metallic oxids, often imparting 
to them characteristic colors. It is used in this way 
in the laboratory, and serves thus as a means of rec- 
ognizing many of the elements. 

165. The Carbon Group. This group comprises 
the non-metallic elements carbon and silicon, to- 
gether with tin and lead, and some rare elements. 
The non-metals are quadrivalent and rarely biva- 
lent ; the metals are bivalent and occasionally quad- 
rivalent. Carbon and silicon are among the most 
important elements known, one or the other being 
found in nearly every naturally occurring compound. 
Carbon is an important constituent of all animal 



114 LECTURE NOTES. 

and vegetable compounds, while silicon bears a sim- 
ilar relation to most of the rocks and soils. Only 
these two elements will be considered at this time. 

Carbon. Symbol, C. Atomic Weight, 12. 

166. History and Occurrence. Carbon, in some 
of its forms, has been known since the very earli- 
est times, although its allotropic modifications were 
not recognized until the end of the last century, 
and its relations to organic chemistry were not 
thoroughly understood until some years later. 

Carbon is a very abundant element, and occurs 
in a greater number of compounds than any other 
known element. It occurs free as diamond, graph- 
ite, and the different varieties of mineral coal. Com- 
bined with other elements, principally hydrogen, 
oxygen, and nitrogen, it is found in all animal and 
vegetable substances, and their derivatives. 
bined with oxygen, it occurs as carbon dioxid in the 
atmosphere, and combined with oxygen and the met- 
als, it forms the carbonates, which constitute quite 
a portion of the earth's crust, and which arc found 
in small quantities in nearly all natural waters. 

167. Preparation and Properties. Carbon is 
formed by the imperfect combustion of organic sub- 
stances. The diamond has never been formed arti- 
ficially and we do not know how it is formed in 
nature. Graphite can be formed by fusing carbon 



LECTURE NOTES. 115 

with iron. A small amount of carbon is dissolved 
in the molten iron, and can be obtained by dissolv- 
ing the iron in some acid. 

Pure carbon (diamond) is a transparent crystal- 
line solid, having a specific gravity of 3.5, and is 
the hardest substance known. Graphite is a black 
crystalline solid, has a specific gravity of 2.2, and 
so soft as to leave a mark on paper. The amorphous 
forms of carbon are all black solids, which vary in 
specific gravity from 1.2 to 2.3, and in hardness from 
charcoal, which is quite soft, to gas carbon which is 
very hard. 

No form of carbon has ever been fused, but in the 
electric arc it volatilizes slightly. The only solvent 
for carbon known is molten iron, which dissolves 
about one per cent. 

Diamond and graphite can be made to combine 
with oxygen, but only at a very high temperature. 
The other forms of carbon do not combine directly 
with any element at ordinary temperatures, but at 
a red heat it combines with oxygen and sulfur, and 
at a white heat the affinity of carbon for oxygen 
and sulfur is so very great, that it becomes one of 
the most powerful reducing agents known. It will 
combine directly with hydrogen at the temperature 
of the electric arc. It combines indirectly with 
most of the elements, particularly with hydrogen, 
oxygen, nitrogen and sulfur, forming an almost 
countless number of compounds, the study of which 



Il6 LECTURE NOTES. 

is confined to that portion of the science called or- 
ganic chemistry, and which, for this reason, is often 
called the " chemistry of .the carbon compounds." 

168. Diamond. The diamond is the rarest, and 
most valuable of mineral gems, and has been high- 
ly regarded for ages on account of its brilliant lus- 
ter, and remarkable hardness. It was formerly be- 
lieved to be a peculiar kind of rock crystal, and 
only at the end of the last century was its real com- 
position known. 

It occurs mostly in alluvial deposits, the princi- 
pal localities being Golconda, in British India, Bra- 
zil, and South Africa. It occurs in crystals with 
more or less curved faces and edges, and which be- 
long to the regular system. It is usually colorless 
or slightly yellow, but is occasionally found colored 
green, blue, or red, and, in an impure form, black. 

The natural brilliancy of the diamond is greatly 
increased by cutting and polishing. This is done by 
means of diamond dust, obtained by crushing small 
and imperfect diamonds known as bort or boart. 
Fragments of boart are used for writing upon and 
cutting glass, and for making the diamond drills 
which are employed in rock-boring. An impure 
black variety of diamond, called carbonado, is also 
used for this purpose. 

The unit of weight for the diamond is the carat. 
This is a very old weight, and is equal to 0.205 
grams, or 3.16 grains. The value of the diamond 



LECTURE NOTES. 117 

increases very rapidly with its size, the increase be- 
ing approximately as the square of its weight. 

169. Graphite. Graphite occurs quite widely 
distributed. It is usually found in compact masses, 
or in hexagonal plates, the principal localities be- 
ing Cumberland, in England, Ceylon, Siberia, and 
in the United States at Sturbridge, Mass., in north- 
ern New York, and in California. It is dark gray 
in color, opaque, and unctuous to the touch. It 
conducts electricity, and is so soft that it makes a 
black streak on paper. It was at first supposed to 
contain lead, and so called plumbago or black lead. 
It does not combine with oxygen except at a very 
high temperature, being quite as difficult to burn 
as the diamond. Its principal uses are in the man- 
ufacture of pencils, crucibles and stove polish. 
Most graphite contains a small percentage of hydro-' 
gen, showing that it is probably of vegetable origin. 

170. Amorphous Carbon. A great number of 
varieties of amorphous carbon exist. . They are all 
black and opaque, but differ much in their physical 
properties. The naturally occurring varieties are 
called coal, while the artificial varieties are classi- 
fied according to their origin, as charcoal, coke, 
gas-carbon and lampblack. They are mostly of 
vegetable origin and contain more or less impuri- 
ties, according to the completeness of the decompo- 
sition of the substances from which they were ob- 
tained. 



Il8 LECTURE NOTES. 

171. Mineral Coal. When vegetable matter de- 
cays in the absence of air, and in the earth, or un- 
der water, a number of gaseous substances are given 
off, and there remains a substance rich in carbon to 
which we give various names, but which, in general, 
we call coal. The different varieties of coal depend 
upon the completeness of the decomposition. That 
which has undergone the most complete decompo- 
sition, and hence has the largest percentage of car- 
bon, is called anthracite. It has a bright, almost 
metallic lustre, and is quite hard. It is found 
principally in Wales and in Pennsylvania. 

The bituminous coals consist of a number of varie- 
ties, all of which burn with a smoky flame, and, on 
distillation, yield a number of volatile hydrocarbons, 
and tar, or bitumen. Cann el coal differs somewhat in 
texture from the preceding, but is similar in com- 
position. 

There are a number of varieties of coal belong- 
ing to a later geological period than those describ- 
ed. These contain from 60 to 80 per cent, of carbon, 
and are used for fuel. The principal ones are bog- 
head coal \ brown coal, and peat, or turf. 

172. Charcoal. This important substance is 
made by the imperfect combustion of wood. Large 
piles of wood are covered with sods and earth, and 
allowed to burn with an insufficient supply of air. 
until all the volatile products are driven off. It is 
a black porous solid and burns without sniok 



LECTURE NOTES. II9 

flame. It absorbs large quantities of gases, espe- 
cially ammonia, and hydrogen sulfid. It is, on this 
account, used for the construction of filters for puri- 
fying drinking water, and as a disinfectant and de- 
odorizer. It is also used for the reduction of ores, 
and for fuel. 

Animal charcoal is prepared by heating bones, and 
other animal refuse, in iron retorts. It consists of 
carbon,« mixed with calcium phosphate, and is large- 
ly used in sugar refineries for clarifying the syrup. 

173. Coke and Gas Carbon. Coke bears the 
same relation to coal as does charcoal to wood. In 
the manufacture of coal gas, bituminous coal is heat- 
ed in retorts, until all the volatile products have 
been driven off, when coke remains. It is also 
made in coke ovens, by burning coal to a certain 
point, and then stopping the combustion. It is a 
gray, lustrous, porous solid, which takes fire at a 
much higher temperature than common coal, and 
burning, gives a very high temperature. It is, used 
in iron smelting. 

Gas carbon is found as a deposit in the upper por- 
tion of the gas retorts, and is an iron gray mass, 
which is very hard, and conducts electricity. It is 
a very pure form of carbon and is used for making 
the carbon plates in batteries, and for the candles 
used in electric lighting. 

174. Lampblack, or Soot. When any compound 



120 LECTURE NOTES. 

rich in carbon, is burned with an insufficient supply 
of air, some of the carbon passes off, forming what 
we call lampblack or soot. Resin, turpentine, or 
crude petroleum may be burned for this purpose. 
It is purified by heating in a closed vessel, although 
after this it still retains hydrogen, which can only 
be removed by long continued heating in a stream 
of chlorin. This is the purest form of amorphous 
carbon, and is used in making Indian ink and 
printer's ink, and also as a pigment. 



COMPOUNDS OF CARBON WITH HYDROGEN. 



175. The Hydrocarbons. Carbon forms an ex- 
tremely large number of compounds with hydrogen. 
These are known as the hydrocarbons, and form a 
number of distinct classes or series. The series 
themselves have many points of likeness, and the 
members of each series are much alike, each high- 
er member being distinguished from the preceding, 
by the increment CH 2 . All of these compounds be- 
long to the division which we call organic chemis- 
try, arid only three of the simplest ones will be con- 
sidered here. These are, 

Methane, CH 4 , 

Ethylene, CgH«, and 

Acetylene, C2H2. 



LECTURE NOTES. 121 

Methane, or Marsh Gas. Molecular formula, CH 4 
Density, 8. 

176. History and Occurrence. Methane has 
been known since very early times. It was not dis- 
tinguished from hydrogen until the latter part of 
the last century, when Volta showed that in burn- 
ing, it required four times as much oxygen as did 
hydrogen, and that it produced carbon dioxid, 
which the hydrogen did not. To distinguish it 
from ethylene, which was the only other hydro- 
carbon known at this time, it was called light car- 
bur etted hydrogen, ethylene being much heavier. 

It occurs free in nature, being formed by the de- 
composition of vegetable matter under water. The 
bubbles of gas which rise when a stagnant pool is 
stirred, consist largely of methane, hence the name 
marsh gas. It is also formed by the slow decompo- 
sition of bituminous coal, forming what the coal 
miners call fire damp. It is the principal ingredi- 
ent in natural gas. 

177. Preparation. Methane is best prepared by 
heating a mixture of sodium acetate and sodium 
hydroxid, the latter being in excess, thus: 

NaC 2 H 3 0, + NaOH == Na 2 COs + CH 4 . 
Thus obtained, it always contains some hydrogen, 
and ethylene. If required pure, it may be obtained 
by decomposing zinc methyl, Zn (CHa)*, by means 
of water. It is produced by the decomposition of 
many organic compounds. 



122 LECTURE NOTES. 

178. Properties. Methane is a colorless, odor- 
less, and tasteless gas. Next to hydrogen, it is the 
lightest gas known. It is combustible, burning 
with a nearly colorless flame, but does not support 
combustion. When mixed with two volumes of 
oxygen, or ten volumes of air, it is very explosive. 
It is this latter mixture which is the cause of the 
terrible explosions which sometimes happen in 
coal mines. When mixed with chlorin and expos- 
ed to direct sunlight, the hydrogen will be partly 
or entirely replaced by the chlorin. 

Ethylene. Molecular formula, C,,H 4 . Density, 14. 

179. History, Occurrence, and Preparation. 
Ethylene was probably discovered by Becher, in the 
middle of the 17th century, although its true com- 
position and properties were not described until 
more than a century later. 

It is found in small quantities in natural gas. and 
is the most important constituent of coal gas, which 
is made by the destructive distillation of coal. 

It is best prepared by the action of a large excess 
of sulfuric acid, upon common, or ethyl alcohol. 
In this action, the acid, abstracts water from the 
alcohol, thus : 

C a H»OH = C_.II, - HO.. 

180. Properties. Ethylene is a colorless 
having a pleasant, ethereal odor. It is a trifle 



LECTURE NOTES. 1 23 

lighter than air, its specific gravity being 0.978. 
It is relatively much heavier than methane, and so 
at first was called heavy carburetted hydrogen. It 
is a combustible gas, burning with a bright, lumin- 
ous flame, and giving some smoke, or unburned car- 
bon. When mixed with three volumes of oxygen 
it is very explosive. 

The most characteristic property of ethylene, is 
its power of combining directly with chlorin to form 
an oily liquid called ethylene dichlorid, C2H4CI2, 
or Dutch liquid, it having been first observed by four 
Dutch chemists. From this property it received the 
name olefiant gas, by which it was for a long time 
known. It can be condensed to a liquid under very 
great pressure, and at a low temperature. 

181. Acetylene. Acetylene is formed by the in- 
complete combustion of many hydrocarbons. When 
the gas in a Bunsen lamp burns at the bottom 
of the tube, acetylene is produced. It is also form- 
ed, when a powerful electric current is passed 
through electrodes of carbon in a vessel contain- 
ing hydrogen. It is best prepared by heating ethy- 
lene dibromid, with a concentrated solution of po- 
tassic hydroxid in alcohol, thus : 

CoH^Br, + 2 KOH = 2 KBr+ 2 H- 2 + C 2 H 2 . 

It is a colorless gas, having a peculiar and disa- 
greeable odor, and is the only hydrocarbon formed 
by direct union of the elements. It is combustible, 
and burns with a luminous, but smoky flame. It 



124 LECTURE NOTES. 

is soluble in its own volume of water, and unil 
directly with the halogens. It is absorbed by an 
ammoniacal solution of a cuprous salt, forming a 
red precipitate, which is explosive. 

182. Illuminating Gas. It was early known 
that when coal was heated, a combustible gas 
produced, but it was not until 1792 that Murd< 
made gas illumination a practical Slice* 

Illuminating gas is ordinarily prepared, by dis- 
tilling bituminous coal at a high temperature. Oth- 
er kinds of coal, as well as wood, and petroleum, are 
sometimes employed, the process being much the 
same. 

The coal is heated in iron retorts, and the vola- 
tile products pass first into a large receiver, where 
tar and some water and ammonia are collected. 
The gas then passes through a purifier, where sul- 
fur compounds, and carbon dioxid are absorbed, 
and then into the gasometer, from whence it is dis- 
tributed in pipes. 

Illuminating gas is a mixture of several gaseous 
products, and varies somewhat according to 
source, and the temperature, at which it is produc- 
ed. The principal ingredients are ethylene, meth- 
ane, and hydrogen, in addition to which it contains 
carbon monoxid, hydrogen sulfid, acetylene, and 
other hydrocarbons. 

The illuminating power of coal-gas, is determined 
by an instrument called ^photometer, in which the 



LECTURE NOTES. 1 25 

amount of light given by the gas when it burns at 
the rate of five cubic feet in an hour, is compared 
with the light of a standard candle, which burns 
120 grains (7.79 grams) of spermaceti per hour. 
Good coal-gas should have from 16 to 20 candle- 
power, or even more. 

183. Combustion. Whenever two substances 
combine chemically, heat is produced. If the at- 
traction of the substances for each other is suffi- 
ciently strong, the heat produced will raise the re- 
sultant substances to a temperature at which they 
will emit light. Such a union is called combustion. 
This term is also used in connection with decay, and 
with the chemical changes which produce animal 
heat. We use the- term slow combustion to indicate 
such changes. 

There are two classes of substances which 
are necessary for a combustion, one is called the 
inflammable, or combustible substance, the oth- 
er the supporter of combustion. We happen to live 
in an atmosphere, the active ingredient of which is 
oxygen ; and so substances which combine with 
oxygen are said to be combustible, and the ox3 7 gen 
is called the supporter of combustion. These terms 
are, however, entirely relative, for while coal-gas 
will burn in the air, or oxygen, oxygen, or air will 
burn in coal-gas. When the combustion takes place 
so rapidly as to be attended with more or less noise, 
we call it explosion. 



126 LECTURE NOTES. 

184. Temperature of Ignition. In order that 
combustion may take place, the combustible sub- 
stance, must be raised to a certain temperature. 
This is called the temperature of ignition, and varies 
widely with different substances. A few compounds, 
such as liquid phosphin, ignite at the ordinary tem- 
perature, when exposed to the air. Phosphorus 
ignites at about 50 , carbon disulfid at 150 , and 
sulfur at 260 , while coal-gas will not ignite at red 
heat, and nitrogen only in the electric arc, the high- 
est known temperature. This principle has been 
utilized, in the safety lamp, invented by Davy, for 
use in coal mines. 

Slow combustion takes place at a much lower 
temperature. Mechanical division increases com- 
bustibility, to such an extent, that the slow com- 
bustion, beginning at the ordinary temperature, of- 
ten raises the temperature to the point of ignition. 
This is the reason why spontaneous combustion 
takes place in heaps of old refuse, especially of oily 
rags, and which is such a common cause of fires. 

185. The Nature of Flame. The combustion of 

substances, may, or may not, be accompanied by 
flame. A non-volatile substance, like carbon, burns 
with a bright glowing, but without flame. A com- 
bustible gas, or a solid or liquid, which, at the tem- 
perature of combustion produces a combustible 
burns with a flame. Flame, then, is gas raised by 
combustion to incandescence. 



LECTURE NOTES. 127 

A flame, may be divided into three parts, — the dark 
central portion of unburned gas, the luminous por- 
tion, or area of incomplete combustion, and the 
outer, or non-luminous portion, in which complete 
combustion has taken place. 

The luminosity of a flame, depends upon the pres- 
ence, in the flame, of solid particles, which are not 
volatile, and which are heated to whiteness by the 
process of combustion. In the ordinary gas, or 
candle flame, these solid particles are unburned car- 
bon. A non-luminous flame, like that of burning 
hydrogen, may be made highly luminous, by intro- 
ducing some solid, like a piece of platinum wire. 
If a vessel be heated in a luminous gas flame, soot 
is deposited. To avoid this, we use, for heating, 
a lamp so constructed as to insure complete com- 
bustion. Such a lamp was invented by Bunsen, 
and is known as the Bunsen burner. 

Since hot carbon combines with oxygen with 
great energy, and so is reducing in its action, the 
luminous gas flame, which it contains unburned car- 
bon, is a reducing flame. The non-luminous gas 
flame, such as that produced by the Bunsen burner, 
is, on the contrary, an oxidizing flame, because it 
contains an excess of heated air or oxygen. 

186. The Halogen Compounds of Carbon. Car- 
bon does not unite with the halogens directly, but 
compounds can be formed by the action of the hal- 
ogen on certain hydrocarbons. In this action, the 



128 LECTURE NOTES. 

halogen replaces the hydrogen, and substitution pro- 
ducts are formed, thus : 

CH 4 + 4 Cl 2 = CCU + 4 HC1. 
A more complete description of these compounds, 
belongs to organic chemistry. 

COMPOUNDS OF CARBON WITH OXYGEN. 

Carbon forms but two oxids. These are, 
Carbon monoxid, CO, and 
Carbon dioxid, CO2. 

Both compounds are gases, and quite important. 

Carbon monoxid. Molecular formula, CO. Den- 
sity, 14. 

187. Occurrence and Preparation. Carbon mon- 
oxid does not occur free in nature, but is produced 
in large quantities by the combustion of carbon in 
an insufficient supply of air. It is the burning of 
this gas that causes the blue flames which may be 
seen whenever coal is burning. 

It is best prepared by heating oxalic acid, with 
concentrated sulfuric acid, which removes water. 
and produces equal volumes of carbon monoxid, 
and carbon dioxid, thus : 

H2C3O4 = H 2 + CO> + C( ). 

The carbon dioxid is removed, by passing the 
gases through a solution of sodium hydroxid. 



LECTURE NOTES. 129 

It is formed by the incomplete combustion of car- 
bon, and also by passing carbon dioxid over red hot 
charcoal, thus : 

C0 2 + C = 2CO. 

188. Properties. Carbon monoxid is a colorless, 
tasteless gas, having a slight, but oppressive odor. 
It is only very slightly soluble in water. It 
is combustible, and burns with a bright, blue 
flame. It is extremely poisonous, producing a se- 
vere headache when present in the air, even in 
small quantities. In larger quantities it produces 
insensibility, and death. ,It is an unsaturated mol- 
ecule, combining easily with oxygen to form car- 
bon dioxid, and is therefore a powerful reducing 
agent. It combines directly with chlorin, produc- 
ing carbon oxychlorid, ox phosgene, COC1-2. 

Carbon Dioxid. Molecular formula, C0 2 . 
Density, 22. 

189. History and Occurrence. Up to the middle 
of the 1 6th century, all gases were supposed to be 
alike, and were called air. Carbon dioxid was 
the first gas to be distinguished from common air. 
It was at first called by various names, such as 
chalky air, fixed air, and, later, carbo?iic acid. 

It occurs free in the atmosphere, of which it con- 
stitutes about 0.04 per cent., being formed by the 
oxidation of all organic substances. It is found in 



130 LECTURE NOTES. 

soils, and in many mineral springs, and not infre- 
quently collects in deep wells, cellars, and coal pits, 
when it is known as choke damp. Combined with ox- 
ygen and the metals, it forms the vast series of com- 
pounds called carbonates, of which the most impor- 
tant one is calcium carbonate, CaC03, which ex- 
ists under the different names of calcite, marble, 
chalk, and limestone. Other carbonates are mag- 
nesite, MgCOs; dolomite, (CaMg)CO: ; siderite, 
FeCOs; and many others. 

190. Preparation. Carbon dioxid is most con- 
venient^ prepared, by the action of some acid up- 
on a carbonate. When marble and hydrochloric 
acid are used, the action is as follows : 

CaC0 3 + 2 HC1 = CaCla + H,0 + CO,. 

It is also produced by heating limestone, in the 
preparation of lime, thus : 

CaCOs = CaO + CO*. 

It is formed whenever wood, coal, or any organic 
substance, is burned in the air, or in oxygen ; or, 
when an organic compound decays ; or, by the pro- 
cesses of fermentation and respiration. 

191. Properties. Carbon dioxid is a colorless 
gas, having a pungent odor, and an acid taste, [t 
is neither combustible nor a supporter of combus- 
tion. It is not poisonous but will destroy life by 
suffocation. Air containing as much as 5 per cent, 
of carbon dioxid may be breathed for a very short 



LECTURE NOTES. 131 

time without serious results, although air contain- 
ing only 0.2 per cent., might prove dangerous to 
life, if breathed continuously. It is much heavier 
than air, its specific gravity being 1.52. 

At a temperature of 15 , water dissolves its own 
volume of this gas. If the pressure be increased, the 
solubility is increased in the same ratio, so that un- 
der ten atmospheres pressure, water dissolves ten 
times as much of the gas^ as under the ordinary 
pressure. There is probably a weak chemical union 
between the carbon dioxid and the water, forming 
an acid, known as carbonic acid, H2CO3. This is 
an extremely unstable compound, but its salts, the 
carbonates, are very stable. It is a dibasic acid, and 
so forms both normal and acid carbonates. 

Carbon dioxid may be condensed to a liquid by a 
pressure of 38.5 atmospheres at o°, and if this liquid 
be allowed to escape through a proper opening, it 
will evaporate so rapidly, that the absorption of 
heat from the remaining portion, will cause it to 
form a snow-white solid, which melts at -65 . If 
this solid carbon dioxid is mixed with ether, and 
allowed to evaporate in a vacuum, a temperature of 
-140 may be obtained. 

Although carbon dioxid is constantly being form- 
ed in the atmosphere, the quantity is never much 
increased. This is because it is the principal plant 
food. The plants absorb carbon dioxid, which is 
decomposed in the cells of the plant leaf, setting 



132 LECTURE NOTES. 

free oxygen. This action in much increased by 
sunlight. 

192. Carbon Disulfid, CS 2 . Carbon disulfid does 
not occur free in nature, but is easily produced syn- 
thetically, by leading the vapor of sulfur over hot 
charcoal in a suitable retort. It is a colorless, vol- 
atile, strongly refracting liquid. When pure, it has 
a pleasant, ethereal odor, which becomes very disa- 
greeable when the compound is impure. Its vapor 
is very inflammable, and takes fire at 150 , burning 
with a blue flame. When mixed with nitric oxid, 
it burns with great brilliancy. It is much used as 
a solvent for phosphorus and sulfur, and for extract- 
ing certain essential oils. 

193. Cyanogen Gas, (CN) 2j or Cy L >. Cyanogen is 
a compound radical which much resembles the ele- 
ments of the halogen group. (See Art. 56). Cy- 
anogen gas bears the same relation to cyanogen, as 
does chlorin gas to an atom of chlorin. It is best 
prepared by heating mercuric cyanid, thus: 

Hg (CN) 2 = Hg + (CN) a . 
It is a colorless gas having a peculiar odor like 
peach kernels. It is somewhat soluble in water. It 
is combustible, burning with a characteristic purple- 
red flame, and is exceedingly poisonous. It forms 
a compound with hydrogen, called hydrocyanic, or 
prussic acid, HCN, and with the metals, forms a 
series of important compounds, called cyanids. The 
cyanids may be regarded as salts of hydrocyanic 



LECTURE NOTES. 1 33 

acid, and much resemble the corresponding halogen 
compounds. 

Silicon. Symbol, Si. Atomic Weight, 28. 

194. Occurrence. Silicon, next to oxygen, is 
the most abundant element in nature. Over 27 per 
cent, of the solidearth is silicon. It is never found 
free in nature, but in combination with oxygen it 
is very abundant, forming quartz, or silica, SiO-2. 
In combination with oxygen and the metals it 
forms the silicates, which constitute the greater 
portion of the solid earth. 

195. Preparation. Silicon is best prepared by 
heating together potassium silico-fluorid, and me- 
tallic potassium, in an iron tube. The action, which 
is quite violent, is as follows : 

K 2 SiF 6 + K 4 = 6 KF + Si. 
The potassium fluorid is then dissolved in water, 
the silicon remaining as an insoluble powder. 

196. Properties. When prepared as above, sili- 
con is a brown amorphous powder, which is insolu- 
ble in all mineral acids, except hydrofluoric acid. 
It has a specific gravity of 2.49. When heated in 
the air, or oxygen, it takes fire and burns, forming 
silicon dioxid. If the amorphous silicon be strong- 
ly heated in the absence of air, it becomes denser, 
and has an appearance much like graphite. If 
amorphous silicon be fused with zinc, it forms dark 



134 LECTURE NOTES. 

glittering, octahedral crystals, which may be ob- 
tained by dissolving the zinc in some acid. Crys- 
tallized silicon is not acted upon by hydrofluoric 
acid, and is oxidized with difficulty in oxy- 
gen. It is so hard as to scratch glass. Silicon 
forms one compound with hydrogen, a gas, SiH-i, 
which, in contact with air, takes fire spontaneously. 

197. The Halogen compounds of Silicon. Silicon 

forms a compound with each of the halogens. Sili- . 
con tetrachlorid is formed by leading chlorin over 
a heated mixture of silicon dioxid, and carbon. 
The action is as follows : 

Si0 2 +2C+2 Cla = 2 CO + SiCh. 

It is a volatile liquid, boiling at 58 . The bro- 
mid and iodid are formed in a similar way, but are 
not of especial importance. The above halogen 
compounds are decomposed by water, forming sili- 
cic acid, and the corresponding halogen acid. 

The fluorid is formed by the action of hydroflu- 
oric acid on silicon dioxid, thus : 

SiOi + 4 HF = 2 H- 2 -f- SiF*. 

Silicon tetrafluorid is a gas, which is formed when 
glass is etched by hydrofluoric acid. (See Art. 8 
It is decomposed by water forming silicic acid, and 
a peculiar compound known as hydrofluo silicic acid, 
or hydrogen silico-fluorid, which forms a well defin- 
ed series of salts, called silico-fluorids. 

198. Silicon Dioxid. or Silica, SiO_>. This is the 



LECTURE NOTES. 1 35 

only compound of these two elements, and occurs 
abundantly in nature, as quartz, or rock crystal, 
and, in an impure form, as sandstone, and sand. 
Quartz is quite often colored by the presence of cer- 
tain metallic oxids, and is then called by the names 
amethyst, agate, jasper, chalcedony, carnelian, onyx, 
etc. An amorphous form of silica is found in na- 
ture and called opal. 

It is formed by burning silicon in the air, or by 
heating silicic acid, thus : 

H 4 Si0 4 = 2 H 2 + SiO-2. 

Quartz occurs as hard, transparent, hexagonal 
crystals, which have a specific gravity of 2.65. It 
also occurs in masses which are crystalline in struc- 
ture, but not in external form. It can be fused 
in the oxj^-lwdrogen flame. When prepared artifi- 
ciall} T silica is a white amorphous powder. 

199. Glass, Porcelain, and Pottery. These im- 
portant commercial products are composed chiefly 
of silicon dioxid. Glass is made by fusing together 
pure sand, or quartz, with some alkaline carbonate, 
and some metallic oxid, which differs with the kind of 
glass. These compounds combine on heating, form- 
ing silicates of the alkali and the metallic oxid, 
which, together with a large amount of free silica, 
constitutes glass. The alkaline carbonate may be of 
sodium or potassium, while the principal oxids 
used are those of calcium, lead, and iron. 



136 LECTURE NOTES. 

Glass is a hard, brittle substance, which is trans- 
parent and may be obtained in almost any shade of 
color by the addition of certain metallic oxids. 

Porcelain and pottery contain kaolin, a silicate of 
aluminum, which renders it opaque and infusible. 

200. The Silicic Acids, and Silicates. If a sili- 
cate is fused with sodium carbonate, a sodium sili- 
cate is formed, which is easily decomposed by hy- 
drochloric acid, with the formation of free silicic 
acid. There are several of these acids. Normal 
silicic acid, HiSiO-i, may be considered the one from 
which all the others are derived. Metasilicic acid, 
H2SiO:3, ma}' be derived from the normal by the re- 
moval of a molecule of water. The polysilicic acids 
may be considered as derived from two or more mol- 
ecules of the normal acid by loss of water. Some 
of them are very complicated. 

They are jelly-like solids, which, when dried, 
form a white, amorphous powder, and at ioq° lose 
all their water, forming silicon dioxid. 

All of these acids form salts which are called 
silicates. All these different silicates are found in 
nature, and constitute the larger portion of the min- 
eral substances found in the earth's crust. The 
more exhaustive study of these compounds, belongs, 
therefore, to the science called mineralogy. 



ERRATA. 

Page 4, 4th line, for cubit, read cubic. 

Page 6, 6th line from bottom, for F° = § C°+ 32, 
read F° = § C° + 32. 

Page 7, 8th line from bottom, for or, read on. 

Page ii, 8th line, for remain, read remaining. 

Page 47, 2d line from bottom, for yellew, read 
yellow. 

Page 53, in first formula, for H 2 0, read 2H0O. 

Page 57, 1 2th line, for know, read known. 

Page 60, 9th line from bottom, for formid, read 
formed. 

Page 97, 3d line from bottom, for derivations, read 
derivatives. 

Page 122, 3d line from bottom, for HO), read HoO. 

Page 123, i6thline, after Acetylene, insert CoH>. 

Page 125, 15th line, for combutsion, read com- 
bustion. 

Page 127, 9th line from bottom, omit "it." 



INDEX. 



Acetylene, 

Acid Boric. .. 

" Carbonic 

" Chloric 

" Hydrazoic 

" Hydriodic 

" Hydrobromic 

'• Hydrochloric 

'• Hydrocyanic 

" Hydrofluoric 

" Hydrofluosilicic 

" Hypophosphorous 

" M taboric .. 

" Nitric .. 

" Nitrous -- 

" Nordhausen 

" Phosphoric 

" " Glacial 

" Phosphorous -. 

" Prussic 

" Pyroboric 

" Pyrosulfuric . 

" Silicic 

" Sulfuric 

" Sulfurous 

" Tetraboric 

" Thiosulfuric 

Acids,. 

" Basicity of. 

" Halogen 

" Oxy 

Action, Chemical 

Adhesion 

Affinity, Chemical 

Air, Chalky, Fixed 

" Marine acid.. 

Alkalies 

Allotropic Forms 

Amido Group 

Ammonia 

Ammonium 

Antimony 

Halogen Comp's of 
" Oxids, and Oxy- 

acids of 

" Sulfur Com]) s of.... 



Analj-sis 

Aqua Fortis 

•' Regia 

Arsenic 

" Halogen Comp's of.. 

" Marsh's test for 

'• Mirror 

" Oxygen Comp's of.. 

'• Sulfur Comp's of 

White 

Arsenolite 

Arsin 

Atmosphere 

Composition of. . 

Atom 

Atomic Attraction 

'■ Value 

" Weight 

Atoms, Electro Positive 

" Electro Negative 

" Weight of 

Avagadro's Law 

Azote 



Barometer 

Base, Definition of... 
Binary- Compounds. . 

Bismuth 

Bleachiug 

" Powder 

Boron 

" Adamantine . 

Borax 

Bort. orBoart 

Brimstone 

Bromiu 

" Oxy acids of 

Buuseu Burner 



Carat... 
Calorie.. 
Ca 



Amorphous . 

Dioxid. 

Disulfid 

Gas. 



138 



Carbon, Group 113 

" Monixid 128 

" Halogen Comp's of_. 127 

Carbonado.. 116 

Carbonates 130 

Charcoal 117,118 

" Animal 119 

Chamber Process 68 

Chemistry, Definition of 2 

" Organic 116 

Chemism 13 

Chemical Notation 19 

Chlorin 42 

" Oxids of 47 

'■ Oxy-acids of 48 

Choke Damp 130 

Coal, Anthracite. 118 

" Bituminous 118 

" Caunel 118 

'• Mineral 118 

Cohesion 9 

Coke 117,119 

Combustion 125 

Crith 28 

Cyanids _. 132 

Cyanogen 132 

Definite Proportions, Law of 14 

Deliquescence 39 

Density... 4 

Diamond 115,116 

Dutch liquid 123 

Efflorescence 39 

Elements, Names and 

Symbols of. 16 

Elements, Classification of. 18 

" Table of 17 

Equations, Chemical 23 

Ethylene 122 

Expansion, Coefficient of .. 5 

Fire Damp 121 

Flame. Nature of. 126 

" Oxydizing 127 

" Reducing. 127 

Fluorin 55 

Force 1 

Formulas. Chemical 19 

Empirical 20 

" Graphic 20 

Gas, Illuminating 124 

Gases, Diffusion of... 4 

Gay I.ussac Tower 69 

Glass 1 ;5 

Glover Tower. 

('.rain 4 

Graphite - 115,117 

Gravitation 1,3 



Halogen Group 41 

Heat, Effects of on mattet. 5 

" Latent n 

" " of steam -7 

" " " water 37 

" Measurement of. 

" Sensible 11 

Hydnizin 82 

Hydrocarbons 120 

Hydrogen 27 

Arsemd 102 

Chlorid 45 

Dioxid 41 

Heavy Carburetted 123 

" Light Carburetted 121 

Sulfid 61 

Hydrogenium 29 

Hydroxyl Group 21 

Ignition. Temperature of.. 1.6 

Imido Group 83 

Iodin 52 

" Oxids of. 54 

" Oxy-acids of... 54 

Kelp 53 

Lampblack 119 

Latent Heat n 

Liter 4 

Liquids, Diffusion of. 4 

Marsh Gas 121 

Marsh's Test for Arsenic. 102 

Mass, Attractions of. 3 

Matter x 

" Divisions of... 3 

'■ Indestructibility of. 2 

Measures .' 

Metals 18 

Metathesis 33 

Meter 

Methane 

Molecules. 

Molecular Attl 8 

Volume 9 

Weight 10 

Multiple proportions, l.aw oi * 

Nascent State. r 4 

Niter. 8g 

Nitric Oxid 85 

u 

I M"\;<! 85 

Halogen Comp's oi 83 

Mouoxid 

88 

Pentoxid.. F8 

87 

»xid 

Trioxid 86 



Nomenclature, Chemical.. 24 

Non-metals 18,27 

Occlusion 29 

Olefiant Gas 123 

Oxydizing Agents 31 

Flame 127 

Oxygen 29 

Ozone 32 

Paris Green to 5 

Peat 118 

Phosgene 129 

Phosph n 95 

Phosphates, Primary 99 

Second 99 

" Tertiary 99 

Phosphorus 91 

" Allotropic Forms of. 94 

" Halogen Comps of.. q6 

" Oxy-acids of 97 

" Red, or Amorphous. 94 

'' Sulfur Comps of 99 

Phosphonium __ 96 

Phosphoresence 93 

Photometer 124 

Physics. Definition of 2 

Plumbago 117 

Porcelain 135 

Pottery 135 

Pressure, Effects on matter 7 

Quartz 135 

Radical, Compound 20 

Reducing Agents 31 

" Flame 127 

SafetyLamp 126 

Salt.Microcosmic 92 

" Spuit of 45 

Salts 22 

" Acid 22 

" Ammomacal 81 



EX. I39 

Salts, Basic 22 

" Normal 22 

" Sulfo 107 

Saltpeter 89 

Science, Departments of... 2 

Selenium 72 

Silicates 136 

Silicon 133 

" Dioxid 134 

" Halogen Comp's of 134 

Solutions 12 

Specific Gravity 4 

Stibin 109 

Stibnite .108,110 

vSulfur 57 

'■ Allotropic Forms of 60 

" Dioxid 64 

'• Flowers of 59 

" Group 57 

" Halogen Comp's of... 63 

" Milk of 61 

'■ Oxv-acids of 66 

" Roll 59 

" Trioxid 65 

Synthesis... 23 

Tartar Emetic 109 

Tellurium 72 

Tension of Aqueous Vapor. 37 

Thermometers.. 5 

Varec 53 

Valence 15 

Ventilation 79 

Water 33 

" Fresh 40 

" Hard and Soft 40 

" Maximum Densit\' of. 30 

" Mineral 40 

" Natural 39 

" of Crystallization 38 

Weight, Atomic 14 

" Molecular 10 

Weights and Measures 3 



